Pick Module.md as the default doc for v2 balas

[azinneera]

Purpose

Pick Module.md as the default doc for v2 balas

Fixes #42981

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 63.15789% with 14 lines in your changes missing coverage. Please review.

Project coverage is 77.46%. Comparing base (4330bae) to head (782e026).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...java/io/ballerina/projects/internal/BalaFiles.java	50.00%	12 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #43642      +/-   ##
============================================
- Coverage     77.47%   77.46%   -0.02%     
- Complexity    58515    58517       +2     
============================================
  Files          3434     3434              
  Lines        218698   218733      +35     
  Branches      28919    28923       +4     
============================================
+ Hits         169441   169442       +1     
- Misses        39858    39893      +35     
+ Partials       9399     9398       -1     

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