Use isIdentifierChar instead of regex for toIdentifier

[mischnic]

Q	A
Fixed Issues?	Fixes #12574
Patch: Bug Fix?	👍
Major: Breaking Change?
Minor: New Feature?
Tests Added + Pass?	Yes
Documentation PR Link
Any Dependency Changes?	Only internal
License	MIT

Non ASCII-chars that are still valid in an identifier were previously removed (so valid identifiers were turned into _). Use isIdentifierChar instead as suggested in #12574 (comment)

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[nicolo-ribaudo]

Can you add a test with a name whose first character is a valid identifier char, but not a valid identifier start?

[mischnic]

@nicolo-ribaudo I've added expect(t.toIdentifier("1bc")).toBe("bc");. I hope that's what you had in mind?

[nicolo-ribaudo]

I was thinking more about something non in the ASCII range, like ҇ (\u0487) which is a valid identifier character but it cannot be the first one.

expect(t.toIdentifier("\u0487a")).toBe(...)

[nicolo-ribaudo]

Thanks!