fix(ast): preserve TS index signature name span instead of discarding

[camchenry]

Doing some downstream work in https://github.com/camchenry/oxc_checker, I noticed that the span for TSIndexSignatureName refers to the entire foo: string, but there's no subspan for the name specifically, even though we do parse this information. See camchenry/oxc_checker@e2105ae for how I'm working around this instead. (This makes it difficult to compare types with tsc, since it has a type for this location, but that's beside the point)

So, this PR changes the type for the name from just plain Str to an actual IdentifierName, which means we store both the Str and the Span for the name. There is a custom ESTree converter added so that we don't change the existing ESTree output however.

[camchenry]

• fix(ast): preserve TS index signature name span instead of discarding #23656 👈 (View in Graphite)
• main

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[codspeed-hq]

Merging this PR will not alter performance

✅ 62 untouched benchmarks
⏩ 9 skipped benchmarks¹

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_{Comparing 06-19-fix_ast_preserve_ts_index_signature_name_span_instead_of_discarding (7b82c04) with main (b1948a1)}

Footnotes

1. 9 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩