celinspector: fix variable scope conflicts and resource detection edg…

…e cases

Fix several edge cases in the CEL inspector around variable scoping and resource detection:

- Fix variable scope conflicts between top-level declarations and loop variables
  (e.g when 'i' is both a declared resource and used as a loop variable in filter)
- Add proper tracking of loop variables to avoid false positives in unknown resource detection
- Fix chain method calls on unknown resources to correctly track the dependency chain
- Handle ambiguous identifiers more robustly in nested scopes
- Add comprehensive test coverage for edge cases and variable conflicts

The changes make the inspector more reliable when dealing with complex expressions
that mix resource references with loop variables and method chains.