Fix change var type code action not working for wild card bindings

[LakshanWeerasinghe]

Purpose

$subject

Fixes #42823

Approach

When extracting variable names from local and module variables, update the implementation to handle wildcard binding patterns.

Samples

https://github.com/ballerina-platform/ballerina-lang/assets/46857198/b8d3c0f4-2c8d-4562-9ed6-453ab2ebec8a

Remarks

List any other known issues, related PRs, TODO items, or any other notes related to the PR.

Check List

• [x] Read the Contributing Guide
• [ ] Updated Change Log
• [ ] Checked Tooling Support (#<Issue Number>)
• [x] Added necessary tests
  • [x] Unit Tests
  • [ ] Spec Conformance Tests
  • [ ] Integration Tests
  • [ ] Ballerina By Example Tests
• [ ] Increased Test Coverage
• [ ] Added necessary documentation
  • [ ] API documentation
  • [ ] Module documentation in Module.md files
  • [ ] Ballerina By Examples