Cache parsed object names (#675)

* Cache parsed object names

Looking up the fstring table isn't that cheap, if we assume most object
names are likely to re-appear, it makes sense to keep a small cache of them on
the stack.

e.g. `[{"foo": 1, "bar": 2}, {"foo": 3, "bar": 4}]`

In term of implementation, we use a simple sorted array with binary search
as it's the most compact and guarantee a decent `O(log n)`, and the comparison
is first done on the string length, an then fallback to `memcmp`.
Compactness is important here because we're allocating on the stack.

There is also some simple heuristic to avoid caching names that aren't
likely to be repeated, such as numerical names or very long names.

This helps quite a bit on `activitypub`, `twitter` and `ctim_catalog` macro-benchmarks.

Before:

```
== Parsing activitypub.json (58160 bytes)
ruby 3.3.4 (2024-07-09 revision be1089c8ec) +YJIT [arm64-darwin23]
Warming up --------------------------------------
                json   714.000 i/100ms
                  oj   801.000 i/100ms
          Oj::Parser   943.000 i/100ms
           rapidjson   632.000 i/100ms
Calculating -------------------------------------
                json      7.135k (± 0.7%) i/s  (140.16 μs/i) -     35.700k in   5.003978s
                  oj      7.991k (± 0.2%) i/s  (125.14 μs/i) -     40.050k in   5.012044s
          Oj::Parser      9.611k (± 0.2%) i/s  (104.04 μs/i) -     48.093k in   5.003723s
           rapidjson      6.318k (± 0.2%) i/s  (158.29 μs/i) -     31.600k in   5.001896s

Comparison:
                json:     7134.7 i/s
          Oj::Parser:     9611.5 i/s - 1.35x  faster
                  oj:     7990.8 i/s - 1.12x  faster
           rapidjson:     6317.6 i/s - 1.13x  slower

== Parsing twitter.json (567916 bytes)
ruby 3.3.4 (2024-07-09 revision be1089c8ec) +YJIT [arm64-darwin23]
Warming up --------------------------------------
                json    57.000 i/100ms
                  oj    62.000 i/100ms
          Oj::Parser    78.000 i/100ms
           rapidjson    56.000 i/100ms
Calculating -------------------------------------
                json    573.527 (± 1.6%) i/s    (1.74 ms/i) -      2.907k in   5.070094s
                  oj    619.368 (± 1.6%) i/s    (1.61 ms/i) -      3.100k in   5.006550s
          Oj::Parser    770.095 (± 0.9%) i/s    (1.30 ms/i) -      3.900k in   5.064768s
           rapidjson    560.601 (± 0.4%) i/s    (1.78 ms/i) -      2.856k in   5.094597s

Comparison:
                json:      573.5 i/s
          Oj::Parser:      770.1 i/s - 1.34x  faster
                  oj:      619.4 i/s - 1.08x  faster
           rapidjson:      560.6 i/s - 1.02x  slower

== Parsing citm_catalog.json (1727030 bytes)
ruby 3.3.4 (2024-07-09 revision be1089c8ec) +YJIT [arm64-darwin23]
Warming up --------------------------------------
                json    31.000 i/100ms
                  oj    34.000 i/100ms
          Oj::Parser    46.000 i/100ms
           rapidjson    38.000 i/100ms
Calculating -------------------------------------
                json    319.842 (± 0.3%) i/s    (3.13 ms/i) -      1.612k in   5.040026s
                  oj    329.315 (± 2.4%) i/s    (3.04 ms/i) -      1.666k in   5.061887s
          Oj::Parser    452.725 (± 1.1%) i/s    (2.21 ms/i) -      2.300k in   5.080996s
           rapidjson    358.160 (± 0.8%) i/s    (2.79 ms/i) -      1.824k in   5.093054s

Comparison:
                json:      319.8 i/s
          Oj::Parser:      452.7 i/s - 1.42x  faster
           rapidjson:      358.2 i/s - 1.12x  faster
                  oj:      329.3 i/s - 1.03x  faster

```

After:

```
== Parsing activitypub.json (58160 bytes)
ruby 3.3.4 (2024-07-09 revision be1089c8ec) +YJIT [arm64-darwin23]
Warming up --------------------------------------
                json   832.000 i/100ms
                  oj   799.000 i/100ms
          Oj::Parser   969.000 i/100ms
           rapidjson   636.000 i/100ms
Calculating -------------------------------------
                json      8.020k (± 0.3%) i/s  (124.70 μs/i) -     40.768k in   5.083607s
                  oj      7.942k (± 1.7%) i/s  (125.92 μs/i) -     39.950k in   5.031909s
          Oj::Parser      9.515k (± 4.4%) i/s  (105.10 μs/i) -     47.481k in   5.001202s
           rapidjson      6.282k (± 2.1%) i/s  (159.20 μs/i) -     31.800k in   5.064719s

Comparison:
                json:     8019.6 i/s
          Oj::Parser:     9514.5 i/s - 1.19x  faster
                  oj:     7941.9 i/s - same-ish: difference falls within error
           rapidjson:     6281.6 i/s - 1.28x  slower

== Parsing twitter.json (567916 bytes)
ruby 3.3.4 (2024-07-09 revision be1089c8ec) +YJIT [arm64-darwin23]
Warming up --------------------------------------
                json    67.000 i/100ms
                  oj    62.000 i/100ms
          Oj::Parser    79.000 i/100ms
           rapidjson    55.000 i/100ms
Calculating -------------------------------------
                json    670.935 (± 2.7%) i/s    (1.49 ms/i) -      3.417k in   5.096850s
                  oj    618.937 (± 3.2%) i/s    (1.62 ms/i) -      3.100k in   5.014800s
          Oj::Parser    768.894 (± 1.7%) i/s    (1.30 ms/i) -      3.871k in   5.036093s
           rapidjson    556.882 (± 2.7%) i/s    (1.80 ms/i) -      2.805k in   5.040970s

Comparison:
                json:      670.9 i/s
          Oj::Parser:      768.9 i/s - 1.15x  faster
                  oj:      618.9 i/s - 1.08x  slower
           rapidjson:      556.9 i/s - 1.20x  slower

== Parsing citm_catalog.json (1727030 bytes)
ruby 3.3.4 (2024-07-09 revision be1089c8ec) +YJIT [arm64-darwin23]
Warming up --------------------------------------
                json    35.000 i/100ms
                  oj    32.000 i/100ms
          Oj::Parser    43.000 i/100ms
           rapidjson    39.000 i/100ms
Calculating -------------------------------------
                json    382.262 (± 2.6%) i/s    (2.62 ms/i) -      1.925k in   5.039336s
                  oj    348.721 (± 0.6%) i/s    (2.87 ms/i) -      1.760k in   5.047265s
          Oj::Parser    478.294 (± 0.6%) i/s    (2.09 ms/i) -      2.408k in   5.034798s
           rapidjson    398.740 (± 0.8%) i/s    (2.51 ms/i) -      2.028k in   5.086365s

Comparison:
                json:      382.3 i/s
          Oj::Parser:      478.3 i/s - 1.25x  faster
           rapidjson:      398.7 i/s - 1.04x  faster
                  oj:      348.7 i/s - 1.10x  slower
```

Author: byroot