fix: quote partition field name in sortBy to handle dotted partition fields (#17425)

[waterWang]

Description

When RewriteManifestsSparkAction.sortBy() is called with a partition field name that contains a dot (e.g., a nested struct field flattened to a.b), the string concatenation in sortColumn() produces col("data_file.partition.a.b"). Spark interprets this as a nested field traversal (partition → a → b) rather than a single field named a.b, causing AnalysisException: [FIELD_NOT_FOUND] No such struct field a in a.b.

Root cause

The sortColumn() method at line 320 builds the Spark column reference by raw string concatenation:

col(DATA_FILE_PARTITION_COLUMN_NAME + "." + p)

When p contains a dot (e.g., a.b), the resulting reference is ambiguous.

Fix

Wrap the partition field name in backticks so Spark treats it as a single literal field name:

col(DATA_FILE_PARTITION_COLUMN_NAME + ".`" + p + "`")

The sibling class FixedWriter (which handles byte[]) already does it correctly.

Affected versions

• spark/v3.5
• spark/v4.0
• spark/v4.1

Testing

The existing tests pass because they use simple partition field names without dots (e.g., c1, c2_trunc, c3_bucket). A test case with a dotted partition field name would trigger the bug.

Closes #17425