Improve the error message for invalid table key values

[nipunayf]

Purpose

The current implementation of checking whether the table key value is a constant expression does not consider its nested expressions. Thus, this PR improves the implementation to precisely capture the value expression of key specifier 'k' must be a constant expression error message.

As mentioned in the specification, a constant-reference expression must reference a module-const-decl, and within a const-expr, any nested expression must also be a const-expr. The existing positive table key field value tests do not adhere to this condition, and this PR updates those test cases with the necessary changes. https://ballerina.io/spec/lang/master/#const-expr

Fixes #35043

Approach

The PR modifies the TypeChecker to improve its implementation of checking the constant expression for table key values.

Remarks

• The table constructor uses a method named isConstExpression that is specific to the table itself. Hence, the changes made by the PR only affect this area. Ideally, this method can be used in other areas as well, and this is tracked with another issue:
• The current implementation does not consider the list constructor spread operator as it is blocked by: [Bug]: An invalid error is generated when using a constant expression in a spread operator #41979
• The current implementation does not consider the xml templates as it is blocked by: [Improvement]: Improve the error reporting of XML templates when used as key values in tables #41985
• The current implementation does not consider the regex templates it is blocked by: [Improvement]: Improve the error reporting of Regex templates when used as key values in tables #41982

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

[codecov]

Codecov Report

Attention: Patch coverage is 83.87097% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 76.70%. Comparing base (9007aa5) to head (9901b72).
Report is 8 commits behind head on master.

Files	Patch %	Lines
...alang/compiler/semantics/analyzer/TypeChecker.java	83.87%	2 Missing and 3 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #41992      +/-   ##
============================================
- Coverage     76.71%   76.70%   -0.01%     
- Complexity    53062    53080      +18     
============================================
  Files          2882     2882              
  Lines        200002   200031      +29     
  Branches      26040    26048       +8     
============================================
+ Hits         153423   153443      +20     
- Misses        38132    38137       +5     
- Partials       8447     8451       +4     

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[github-actions]

This PR has been open for more than 15 days with no activity. This will be closed in 3 days unless the stale label is removed or commented.

[github-actions]

This PR has been open for more than 15 days with no activity. This will be closed in 3 days unless the stale label is removed or commented.