Introduce using slices instead of locations

[kddnewton]

In the C API, we want to use slices instead of locations in the AST. In this case a "slice" is effectively the same thing as the location, expect it is represented using a 32-bit offset and a 32-bit length. This will cut down on half of the space of all of the locations in the AST.

I am introducing this as a new field type to ease the migration path, so that this can be merged on its own and then fields can be moved one at a time.

Note that from the Ruby/Java/JavaScript side, this is effectively an invisible change. This only impacts the C/Rust side.

Fixes #1566

[Earlopain]

I am introducing this as a new field type to ease the migration path, so that this can be merged on its own and then fields can be moved one at a time.

Can you explain this a bit? To me it seems most convenient to have it done relatively quickly so that consumers don't have to bother with both variants.

Eventually this needs changes in ruby/ruby to compile which will make backporting prism versions a bit annoying, so it would be nice if its not spread across many commits in ruby/ruby I think

[froydnj]

(For posterity, linking this to #1566 .)

[kddnewton]

Can you explain this a bit? To me it seems most convenient to have it done relatively quickly so that consumers don't have to bother with both variants.

Yeah this is a good point. Let's just keep it around for the lifetime of this PR while things get migrated, and then we can squash it all before merge.

[kddnewton]

Just to put this explicitly: not merging this until after Christmas/Ruby 4.0 is released.

[Earlopain]

Continues in ruby/ruby#15979 for the CRuby changes

[eregon]

Very nice to see this done, I recall trying and basically failing, it was lots of non-trivial work.