Add quick pick support to infer sub expressions in extract to constant code action

[TharushiJay]

Purpose

This PR adds support for quick picks in the VSCode plugin to identify the sub expression selected by a user when extracting a complex expression to a constant using the extract to constant code action.

PR to the VSCode plugin : https://github.com/wso2-enterprise/ballerina-plugin-vscode/pull/559

Fixes #37480

Samples

https://user-images.githubusercontent.com/27485094/195769926-b69cacb8-5d9b-467d-b75c-7a65e9f64545.mov

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