Add "proxy script" to be able to run bal in Windows Git Bash

[Shadow-Devil]

Purpose

When running bal inside Windows Git Bash the command is not found. This PR adds a "proxy script" that will execute the bal.bat file in Git Bash.

Fixes #13448

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

All modified and coverable lines are covered by tests ✅

Please upload report for BASE (installer-fix@f392e37). Learn more about missing BASE report.

Additional details and impacted files

@@               Coverage Diff                @@
##             installer-fix   #43481   +/-   ##
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  Coverage                 ?   77.55%           
  Complexity               ?    58732           
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  Files                    ?     3447           
  Lines                    ?   219716           
  Branches                 ?    28943           
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  Hits                     ?   170395           
  Misses                   ?    39899           
  Partials                 ?     9422           

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[keizer619]

@Shadow-Devil do this change here?
https://github.com/ballerina-platform/ballerina-update-tool/tree/master/resources/bin

because bin/bal has the content from update tool (which is from above location) and things in the ballerina-lang are being packed inside distributions/bin

'bin/bal' calls the distributions/bin/bal by checking the command