[Debugger] Fix variable value representation and evaluation support for regex variables

[NipunaRanasinghe]

Purpose

This PR fixes the variable representation and, expression evaluation support for Ballerina regex variables.

Fixes https://github.com/ballerina-platform/ballerina-lang/issues/42636

Samples

Now, the regular expression variables are correctly represented under the debugger variable view as follows.

Check List

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