fix: properly strip -- comments and convert tabs to spaces in sqlparse.format

[label-hook]

Summary

Fixes two issues in sqlparse.format() when using strip_comments=True and reindent=True:

1. -- style comments were not being properly stripped
2. Tab characters were not being converted to spaces during reindentation

Closes #23

Changes

Comment Stripping Fix (sqlparse/filters/others.py)

• Modified StripCommentsFilter._process() to properly handle single-line comments (--)
• Added logic to completely remove T.Comment.Single tokens instead of just replacing content
• Ensures all -- comments are fully stripped when strip_comments=True

Tab Normalization Fix (sqlparse/filters/reindent.py)

• Enhanced ReindentFilter._process() to convert tab characters to spaces
• Added tab-to-space conversion logic that respects the configured indent width
• Ensures consistent space-based indentation when reindent=True

Testing

• Created comprehensive test cases covering both issues
• Verified that SQL with -- comments are completely removed when strip_comments=True
• Confirmed that tab characters are properly converted to spaces during reindentation
• Tested with the original issue.sql file to ensure both problems are resolved
• All existing tests continue to pass, ensuring no regressions

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Closes #23