Add a grammar test for TSQL

[lppedd]

This PR adds a test for the TSQL grammar, probably the largest grammar you can find in the ANTLR Grammars repository.

The generated file is so big it causes a o.j.o.objectweb.asm.MethodTooLargeException from the Kotlin compiler when targeting the JVM, so the testing is enabled only for the JS platform for now.

I will report MethodTooLargeException in YouTrack soon.

[lppedd]

As expected it is failing on the JVM. Let's keep this PR parked.

[lppedd]

@KvanTTT FYI

[lppedd]

@ftomassetti to recap the commits here:

• first commit adds a JS and a Native grammar test for the TSQL grammar.
  The test cannot be common because on the JVM compilation fails with MethodTooLargeException.
• second commit filters out the TSql* generated files from the JVM compilation, since we don't need them.
  This means the other phases now complete correctly.
• third commit fixes a strange compiler error that happens only with the TSQL grammar.
  It probably depends on the size of the compiled code.
• fourth commit actually fixes a bug I found accidentally. RuleContext.ruleIndex should have never been mutable.

I think we can merge as testing with a grammar this large will save us from many other issues in the future.

[ftomassetti]

Thank you @lppedd and @KvanTTT

I added minor comments