feat(snowflake): transpile Snowflake IDENTIFIER function to DuckDB

[fivetran-kwoodbeck]

Snowflake's IDENTIFIER(), which resolves a string to a runtime identifier, previously fell through to exp.Anonymous. This folds it into a typed exp.Identifier node (flagged with identifier_func=True) so the Snowflake generator reconstructs IDENTIFIER('name') and the DuckDB generator emits a native identifier. It includes splitting dot-qualified names like IDENTIFIER('t1.col') into a proper exp.Dot chain.

Non-foldable args like IDENTIFIER($var) remain as exp.Anonymous so they round-trip correctly.

Behavior

Snowflake input	DuckDB output
IDENTIFIER('col')	col
IDENTIFIER('t1.col')	t1.col
IDENTIFIER('"Col"')	"Col"
IDENTIFIER($var)	IDENTIFIER($var)

[github-actions]

SQLGlot Integration Test Results

✅ All tests passed

Comparing:

• this branch (sqlglot:transpile/snowflake-identifier-function @ sqlglot 0853a80)
• baseline (main @ sqlglot a76439c)

Overall

main: 192441 total, 153536 passed (pass rate: 79.8%)

sqlglot:transpile/snowflake-identifier-function: 110922 total, 110162 passed (pass rate: 99.3%)

Transitions:
No change

Dialect pair changes: 0 previous results not found, 1 current results not found

✅ All tests passed