Fix(optimizer): infinite recursion in the resolver

[georgesittas]

Closes #7732

[georgesittas]

This is the stack that shows the execution flow leading to the infinite recursion:

  File "/Users/georgesittas/Dev/sqlglot/sqlglot/optimizer/resolver.py", line 182, in get_source_columns
    col_type = self._get_unnest_column_type(explode_col, source.parent)
  File "/Users/georgesittas/Dev/sqlglot/sqlglot/optimizer/resolver.py", line 380, in _get_unnest_column_type
    table_identifier = parent_resolver.get_table(column)
  File "/Users/georgesittas/Dev/sqlglot/sqlglot/optimizer/resolver.py", line 45, in get_table
    table_name = self._get_table_name_from_sources(column_name)
  File "/Users/georgesittas/Dev/sqlglot/sqlglot/optimizer/resolver.py", line 234, in _get_table_name_from_sources
    self._get_all_source_columns()
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
  File "/Users/georgesittas/Dev/sqlglot/sqlglot/optimizer/resolver.py", line 220, in _get_all_source_columns
    source_name: self.get_source_columns(source_name)
                 ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
  File "/Users/georgesittas/Dev/sqlglot/sqlglot/optimizer/resolver.py", line 182, in get_source_columns
    col_type = self._get_unnest_column_type(explode_col, source.parent)
  ...

Both the happy and the unhappy paths work fine now, as demonstrated by the added tests & existing LATERAL EXPLODE tests passing.

[github-actions]

SQLGlot Integration Test Results

✅ All tests passed

Comparing:

• this branch (sqlglot:jo/fix_recursion_issue_resolver @ sqlglot cbb7255)
• baseline (main @ sqlglot df507aa)

Overall

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

sqlglot:jo/fix_recursion_issue_resolver: 180247 total, 142391 passed (pass rate: 79.0%)

Transitions:
No change

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

✅ All tests passed