fix(optimizer): robust scope for UDTF

[geooo109]

For the cases where we have a UDTF and we have to avoid collecting it if it's not a source.

There are cases such as the following

SELECT ... FROM ... WHERE x IN UNNEST(...)

where udtf doesn't work as a source.

[github-actions]

SQLGlot Integration Test Results

Comparing:

• this branch (sqlglot:geooo109/udtf_scope, sqlglot version: geooo109/udtf_scope)
• baseline (main, sqlglot version: 0.0.1.dev1)

By Dialect

dialect	main	sqlglot:geooo109/udtf_scope	transitions	links
bigquery -> bigquery	24643/24648 passed (100.0%)	23495/23495 passed (100.0%)	No change	full result / delta
bigquery -> duckdb	867/1154 passed (75.1%)	0/0 passed (0.0%)	Results not found	full result / delta
duckdb -> duckdb	5823/5823 passed (100.0%)	0/0 passed (0.0%)	Results not found	full result / delta
snowflake -> duckdb	1063/1961 passed (54.2%)	0/0 passed (0.0%)	Results not found	full result / delta
snowflake -> snowflake	65133/65133 passed (100.0%)	63027/63027 passed (100.0%)	No change	full result / delta
databricks -> databricks	1370/1370 passed (100.0%)	1370/1370 passed (100.0%)	No change	full result / delta
postgres -> postgres	6042/6042 passed (100.0%)	6042/6042 passed (100.0%)	No change	full result / delta
redshift -> redshift	7101/7101 passed (100.0%)	7101/7101 passed (100.0%)	No change	full result / delta

Overall

main: 113232 total, 112042 passed (pass rate: 98.9%), sqlglot version: 0.0.1.dev1

sqlglot:geooo109/udtf_scope: 101035 total, 101035 passed (pass rate: 100.0%), sqlglot version: geooo109/udtf_scope

Transitions:
No change

Dialect pair changes: 0 previous results not found, 3 current results not found

✅ 32 test(s) passed