[Refactoring] Mark fields as final if they are not reassigned

[Shadow-Devil]

Purpose

Fields that are not reassigned should be marked as final to make the intent clear. It also helps to later convert some classes to records and encapsulate public fields (use getters & setters).

Approach

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

Samples

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

Remarks

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

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 68.91386% with 83 lines in your changes missing coverage. Please review.

Project coverage is 77.49%. Comparing base (b45e1e1) to head (465d1da).
Report is 17 commits behind head on master.

Files with missing lines	Patch %	Lines
...ntime/transactions/TransactionResourceManager.java	0.00%	23 Missing ⚠️
...llerinalang/docgen/docs/BallerinaDocGenerator.java	12.50%	21 Missing ⚠️
.../runtime/transactions/TransactionLocalContext.java	0.00%	7 Missing ⚠️
...main/java/io/ballerina/cli/utils/TokenUpdater.java	0.00%	5 Missing ⚠️
.../ballerina/runtime/observability/tracer/BSpan.java	0.00%	4 Missing ⚠️
...llerina/runtime/internal/scheduling/Scheduler.java	81.25%	2 Missing and 1 partial ⚠️
...ballerinalang/natives/NativeElementRepository.java	0.00%	2 Missing ⚠️
...llerinalang/util/BackendCodeGeneratorProvider.java	0.00%	2 Missing ⚠️
...g/ballerinalang/util/EmbeddedExecutorProvider.java	0.00%	2 Missing ⚠️
...rinalang/compiler/packaging/repo/PathBalaRepo.java	0.00%	2 Missing ⚠️
... and 10 more

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #43028      +/-   ##
============================================
- Coverage     77.51%   77.49%   -0.02%     
+ Complexity    58585    58575      -10     
============================================
  Files          3438     3438              
  Lines        219219   219196      -23     
  Branches      28921    28910      -11     
============================================
- Hits         169921   169873      -48     
- Misses        39884    39909      +25     
  Partials       9414     9414              

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[SasinduDilshara]

Other than #43028 (comment) LGTM

[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.

[github-actions]

Closed PR due to inactivity for more than 18 days.

[NipunaRanasinghe]

@MaryamZi @SasinduDilshara it seems this PR got closed due to inactivity. So we might need to re-open this and continue reviewing?

[Shadow-Devil]

Failing testcase in Ballerina Distribution:

Output Verification 'time-formatting-and-parsing'
Failed due to output did not match. Line 3: Civil string representation: 2021-04-12T23:20:50.520+05:30
WARNING: This command is deprecated and will be removed in a future release. Use `bal new .` instead
Building example 'time-formatting-and-parsing'
Created new package 'test'.
Compiling source
	runner/test:0.1.0

Running Tests

	test

	testFunc: has failed.

error: there are test failures

		[fail] testFunc:

		    error {ballerina/test:0}TestError ("Assertion Failed!
			 
			expected: 'Civil string representation: 2021-04-12T17:50:50.520Z'
			actual	: 'Civil string representation: 2021-04-12T23:20:50.520+05:30'
			 
			Diff	:
			
			--- actual
			+++ expected 
			 
			 @@ -1,1 +1,1 @@ 
			 
			 -Civil string representation: 2021-04-12T23:20:50.520+05:30
			+Civil string representation: 2021-04-12T17:50:50.520Z
			")
				callableName: createBallerinaError moduleName: ballerina.test.0 fileName: assert.bal lineNumber: 41
				callableName: assertEquals moduleName: ballerina.test.0 fileName: assert.bal lineNumber: 109
				callableName: testFunc moduleName: runner.test$test.0.tests.time_formatting_and_parsing_test fileName: tests/time_formatting_and_parsing_test.bal lineNumber: 79
				callableName: testFunc$lambda0$ moduleName: runner.test$test.0.tests.test_execute-generated_1 fileName: tests/test_execute-generated_1.bal lineNumber: 4
			


		0 passing
		1 failing
		0 skipped

		Test execution time : 0.145s

This is not related to this PR since it also happened in #42955

[NipunaRanasinghe]

Bindgen tool related changes LGTM