Add line and block comment support

[SanjanaBoggaramJ]

Summary

• Adds LINE_COMMENT (--) and BLOCK_COMMENT (/* */) lexer terminals, %ignore'd, per the N1QL comments spec.
• Both exclude a leading '+' so existing hint-comment syntax (/*+ ... */, --+ ...) is unaffected.
• Removes the old comment/block_comment rules — unreferenced and only matched an empty comment body.
  Solves the COMMENT issue mentioned in Few Queries not handled in the parser #6

Test plan

• Added test_line_comment and test_block_comment covering leading, trailing, inline, multiline, and empty comments.
• Confirmed hint-comment syntax unaffected (found a separate pre-existing bug there, unrelated to this change).
• Full existing test suite passes with no regressions.