Add comment option to splitCsv operator (#6705)

[oqadiSAK]

Add support for comments in CSV and TSV files when using the splitCsv() operator.

Closes #6705

Changes

• Add comment option to splitCsv() operator
• Lines starting with the comment character are skipped entirely
• Text following the comment character mid-line is ignored
• Must be a single character (e.g., #, ;)
• Disabled by default to maintain backward compatibility

Note: While RFC 4180 does not define a comment standard for CSV, this implementation follows pandas' read_csv() behavior as a widely-adopted convention: single character only, and comments affect both line-start and mid-line positions.

Example usage:

channel.of('# comment\na,b,c\nd,e # inline comment')
    .splitCsv(comment: '#')
    .view()

Output:

[a, b, c]
[d, e ]

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