Fix Error Message Bug - Add User Friendly String Representation for NodeKind

[krutip7]

Purpose

Describe the problems, issues, or needs driving this feature/fix and include links to related issues.

• Fixes [Bug]: Invalid error message: must be resource function instead of resource_func #43815

• Updates the generated error message by replacing the keyword resource_func with a more user friendly string resource function

Approach

Describe how you are implementing the solutions along with the design details.

• Enhanced the NodeKind enum with custom string representation for user friendly messages

Samples

Provide high-level details about the samples related to this feature.

• Here is a sample image of the existing bug (same as attached to the issue)

Remarks

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

• While the changes in this PR have been limited to the scope of the issue (i.e. the RESOURCE_FUNC enum), it could be extended further to include custom labels for the other enums as well.

Check List

• Read the Contributing Guide
• Updated Change Log
• Checked Tooling Support (#)
• Added necessary tests
  • 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

[CLAassistant]

All committers have signed the CLA.