[Enhancement] Support CSV header row for EXPORT and INSERT INTO FILES

[tracymacding]

This PR adds support for including a header row in CSV file exports:

1. EXPORT statement: Add with_header property to include column names as the first row in exported CSV files. Example: EXPORT TABLE t TO "path" PROPERTIES ("with_header" = "true")

2. INSERT INTO FILES: Add csv.include_header property for the same functionality when using INSERT INTO FILES with CSV format. Example: INSERT INTO FILES ("format"="csv", "csv.include_header"="true", ...)

Changes:

• FE: Add property parsing in ExportStmt, ExportJob, ExportSink
• FE: Add csv.include_header support in TableFunctionTable
• BE: Add header writing logic in PlainTextBuilder for EXPORT
• BE: Add header writing logic in CSVFileWriter for INSERT INTO FILES
• Thrift: Add with_header field to TExportSink
• Thrift: Add csv_include_header field to TTableFunctionTable

Why I'm doing:

What I'm doing:

Fixes #issue

What type of PR is this:

• [ ] BugFix
• [x] Feature
• [ ] Enhancement
• [ ] Refactor
• [ ] UT
• [ ] Doc
• [ ] Tool

Does this PR entail a change in behavior?

• [ ] Yes, this PR will result in a change in behavior.
• [x] No, this PR will not result in a change in behavior.

If yes, please specify the type of change:

• [ ] Interface/UI changes: syntax, type conversion, expression evaluation, display information
• [ ] Parameter changes: default values, similar parameters but with different default values
• [ ] Policy changes: use new policy to replace old one, functionality automatically enabled
• [ ] Feature removed
• [ ] Miscellaneous: upgrade & downgrade compatibility, etc.

Checklist:

• [x] I have added test cases for my bug fix or my new feature
• [ ] This pr needs user documentation (for new or modified features or behaviors)
  • [ ] I have added documentation for my new feature or new function
• [ ] This is a backport pr

Bugfix cherry-pick branch check:

• [x] I have checked the version labels which the pr will be auto-backported to the target branch
  • [ ] 4.0
  • [ ] 3.5
  • [ ] 3.4
  • [ ] 3.3

---

[!NOTE] Adds optional CSV header rows, wiring FE properties through Thrift to BE writers for EXPORT and INSERT INTO FILES.

• Frontend:
  • ExportStmt/ExportJob/ExportSink: parse with_header, collect column_names, and pass via TExportSink.
  • TableFunctionTable: parse csv.include_header for INSERT INTO FILES and set in TTableFunctionTable.
• Backend:
  • ExportSinkOperator: build PlainTextBuilder with header options from TExportSink.
  • PlainTextBuilder: add with_header and column_names options; write header on init; ensure header on finish().
  • CSVFileWriter: add include_header option (parsed in factory) and write header row.
  • table_function_table_sink: propagate csv.include_header to CSV writer options.
• Thrift:
  • TExportSink: add column_names and with_header.
  • TTableFunctionTable: add csv_include_header.
• Tests:
  • Add exec/plain_text_builder_test.cpp; register in be/test/CMakeLists.txt.

^{Written by Cursor Bugbot for commit c13a357facfd0915679f203a5c9d9f1ca5a94d0d. This will update automatically on new commits. Configure here.}

[mergify[bot]]

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[github-actions[bot]]

[FE Incremental Coverage Report]

:x: fail : 10 / 22 (45.45%)

file detail

	path	covered_line	new_line	coverage	not_covered_line_detail
:large_blue_circle:	com/starrocks/load/ExportJob.java	0	6	00.00%	[466, 467, 468, 469, 470, 472]
:large_blue_circle:	com/starrocks/planner/ExportSink.java	0	6	00.00%	[60, 61, 73, 76, 80, 136]
:large_blue_circle:	com/starrocks/catalog/TableFunctionTable.java	1	1	100.00%	[]
:large_blue_circle:	com/starrocks/sql/ast/ExportStmt.java	9	9	100.00%	[]

[alvin-celerdata]

@cursor review

[sonarqubecloud[bot]]

Quality Gate passed

Issues
3 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[github-actions[bot]]

[Java-Extensions Incremental Coverage Report]

:white_check_mark: pass : 0 / 0 (0%)

[github-actions[bot]]

[BE Incremental Coverage Report]

:x: fail : 0 / 20 (00.00%)

file detail

	path	covered_line	new_line	coverage	not_covered_line_detail
:large_blue_circle:	src/exec/plain_text_builder.cpp	0	12	00.00%	[27, 28, 48, 49, 50, 51, 52, 54, 55, 56, 57, 58]
:large_blue_circle:	src/exec/pipeline/sink/export_sink_operator.cpp	0	8	00.00%	[112, 113, 114, 116, 117, 118, 119, 123]

[alvin-celerdata]

@cursor review