[Java 21] Remove Gson usage from Testerina Runtime

[ravinperera00]

Purpose

This allows for the removal of com.google.gson dependency from Ballerina-rt.

Fixes #43416

Approach

Implement the lost functionality using internal alternatives.

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

[HindujaB]

Suggested change

	Object jsonObj = JsonUtils.parse(br, JsonUtils.NonStringValueProcessingMode.FROM_JSON_STRING);
	BMap<BString, Object> testSuiteMap = (BMap<BString, Object>) jsonObj;
	BMap<BString, Object> testSuiteMap = (BMap<BString, Object>) JsonUtils.parse(br,
	JsonUtils.NonStringValueProcessingMode.FROM_JSON_STRING);

Because we only use jsonObj in one place.