[spark] Support Parquet format in COPY INTO

[JunRuiLee]

This PR adds Parquet format support for COPY INTO import and export, as part of #8005.

Changes

Import (COPY INTO table FROM path):

• Read Parquet files with native typed schema (no string-then-cast like CSV/JSON)
• Column matching by name (case-insensitive), not by position
• Extra source columns are ignored; missing columns become NULL
• Cast validation: detects non-null → null after casting (type incompatibility)
• Supports explicit column list, PATTERN, FORCE, ON_ERROR = ABORT_STATEMENT

Export (COPY INTO path FROM table):

• Write Parquet files via df.write.parquet()
• COMPRESSION option (SNAPPY, GZIP, NONE, etc.)

Refactoring:

• Extract resolveDefaultColumn() shared helper (was duplicated in Parquet and text paths)
• Unify recordHistoryAndBuildResults() to accept a countDf parameter (eliminates ~45 lines of copy-paste between Parquet and text paths)
• Add logWarning when default value expression parsing fails (was silently swallowed)

Tests

12 new tests covering: basic import, column name matching, explicit column list, export, export with compression, round-trip, extra fields ignored, missing fields become null, FORCE=FALSE dedup, PATTERN filtering, unsupported option error, rows_loaded count accuracy.

[JingsongLi]

+1