Update go, golangci-lint and action versions.

Address new lint failures flagged by updated golangci-lint version.

Adds support for `Object.values()`

Add support for trailing comma after the last argument of a method call.

Fix the checks for ID_Start & ID_Continue to match the definitions in
https://www.unicode.org/reports/tr31/

In the specific corner case where a regex contains a flag but is not
followed by any symbols, the ast.RegExpLiteral.Literal value would drop
(part of) that flag.

This happens because the p.next() call during the parsing of the flag
wouldn't actually advance the p.chrOffset, and thus endOffset would be
erroneously adjusted.

The fix is just to use the current p.chrOffset and then call p.next()
afterwards.