[Refactoring] Replace normal switches with enhanced switch expressions

[Shadow-Devil]

Purpose

Many existing switch statements are essentially simulations of switch expressions, where each arm either assigns to a common target variable or returns a value. Expressing this as a statement is roundabout, repetitive, and error-prone.

Java 14 added support for switch expressions, which provide more succinct and less error-prone version of switch.
See also: https://sonarcloud.io/organizations/ballerina-platform/rules?languages=java&open=java%3AS5194&q=switch+expression
Partly also fixes: https://sonarcloud.io/organizations/ballerina-platform/rules?open=java%3AS6208&rule_key=java%3AS6208

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 70.18662% with 655 lines in your changes missing coverage. Please review.

Project coverage is 77.36%. Comparing base (39c7a3d) to head (1ca947f).
Report is 64 commits behind head on master.

Files with missing lines	Patch %	Lines
...a/io/ballerina/runtime/internal/TypeConverter.java	32.69%	28 Missing and 7 partials ⚠️
...llerinalang/compiler/semantics/analyzer/Types.java	67.67%	14 Missing and 18 partials ⚠️
...lerina/compiler/api/impl/symbols/TypesFactory.java	31.81%	27 Missing and 3 partials ⚠️
...mpiler/semantics/analyzer/ConstantTypeChecker.java	37.20%	21 Missing and 6 partials ⚠️
...va/org/ballerinalang/formatter/core/Formatter.java	18.18%	26 Missing and 1 partial ⚠️
...ava/io/ballerina/runtime/internal/TypeChecker.java	82.06%	7 Missing and 19 partials ⚠️
...java/io/ballerina/runtime/api/utils/TypeUtils.java	8.00%	22 Missing and 1 partial ⚠️
...rinalang/compiler/semantics/model/SymbolTable.java	52.38%	18 Missing and 2 partials ⚠️
...llerina/compiler/internal/parser/SyntaxErrors.java	89.41%	13 Missing and 5 partials ⚠️
...g/wso2/ballerinalang/compiler/desugar/Desugar.java	60.46%	13 Missing and 4 partials ⚠️
... and 85 more

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #42955      +/-   ##
============================================
+ Coverage     77.34%   77.36%   +0.02%     
- Complexity    58589    58594       +5     
============================================
  Files          3460     3460              
  Lines        219867   219650     -217     
  Branches      28917    28918       +1     
============================================
- Hits         170050   169937     -113     
+ Misses        40399    40300      -99     
+ Partials       9418     9413       -5     

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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.

[Shadow-Devil]

Remove stale status

[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.

[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
Created new package 'test'.
Building example 'time-formatting-and-parsing'
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 : 0.147s

I dont think this is related to this PR