[Bug] [Spark] Scan output ordering fails for special primary-key names #10657

Problem and environment

PaimonScan.outputOrdering passes raw primary-key names to Expressions.identity. Spark parses this argument as a multipart SQL identifier, so valid top-level names containing # or a backtick cause a ParseException, and a name such as a.b is interpreted as a nested field and causes an AnalysisException.

This differs from #5439: that fix quotes the bucket expression, but not the primary-key identity expressions used for output ordering.

Minimal reproduction

Configure a Paimon catalog named paimon, then run:

SET spark.sql.sources.v2.bucketing.enabled=true;
SET spark.paimon.scan.preserve-data-grouping=true;
CREATE TABLE paimon.default.ordering_repro (
  seq INT,
  `#event_id` STRING
) USING paimon
TBLPROPERTIES (
  'primary-key'='seq,#event_id',
  'bucket-key'='seq',
  'bucket'='1'
);
INSERT INTO paimon.default.ordering_repro VALUES (1, 'b'), (1, 'a'), (2, 'a');
SELECT seq, `#event_id` FROM paimon.default.ordering_repro;

Expected: the three inserted rows. Actual: query planning fails in Expressions.identity -> PaimonScan.outputOrdering with a syntax error at #.