Add new `oneOf` compound scope type

[pokey]

Not sure if oneOf is the right name, but we should support a way to compose scope types like the following:

interface OneOfScopeType {
    type: "oneOf";
    scopeTypes: ScopeType[]
}

Then we can construct a OneOfScopeHandler that will behave the same as a hierarchical scope where each scope can be any of scopeTypes. So basically:

• getScopesTouchingPosition: return smallest scopes of any of scopeTypes touching position
• getScopesOverlappingRange: call getScopesOverlappingRange on all scopeTypes and then remove any scopes that are contained by another scope
• getScopeRelativeToPosition: pick first scope of any of the scopeTypes, then skip it for offset > 1, etc
• iterationScope: apply oneOf to the iteration scopes of scopeTypes

Use cases

• Add a proper scope type for "inside" #1046
• Create a smarter iteration scope for "item" #1047
• defining "name" as a union of "class name", "function name", etc
• to define iteration scope of surrounding pair to be union of "inside" and "file"
• users could map a custom scope type Talon side that constructs an oneOf scope type to enable them to construct their own unions of other scope types
• we could maybe map a spoken form "<scope> or <scope>" to construct these on the fly, eg "take next funk or class"

Possible names

• cascading
• union
• oneOf
• anyOf
• or

[AndreasArvidsson]

anyOf it sounds like it's okay for multiple of them to pass/run. oneOf would be my preferred name.