[2201.12.x]Reduce memory usage of holding BIR and source files

[heshanpadmasiri]

Purpose

Port #44185 to 12.x

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 80.71749% with 43 lines in your changes missing coverage. Please review.

Project coverage is 77.27%. Comparing base (08a9351) to head (ca0fe90).
Report is 1 commits behind head on 2201.12.x.

Files with missing lines	Patch %	Lines
...a/io/ballerina/projects/internal/ProjectFiles.java	50.00%	11 Missing and 1 partial ⚠️
...er/packaging/converters/FileSystemSourceInput.java	0.00%	9 Missing ⚠️
...wso2/ballerinalang/programfile/BIRPackageFile.java	55.55%	8 Missing ⚠️
...java/io/ballerina/projects/internal/BalaFiles.java	54.54%	5 Missing ⚠️
...lang/repository/fs/GeneralFSPackageRepository.java	0.00%	5 Missing ⚠️
...a/runtime/internal/types/semtype/BListSubType.java	97.05%	1 Missing and 1 partial ⚠️
.../java/io/ballerina/projects/MdDocumentContext.java	80.00%	1 Missing ⚠️
...va/io/ballerina/tools/text/StringTextDocument.java	95.65%	1 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff               @@
##             2201.12.x   #44188      +/-   ##
===============================================
- Coverage        77.29%   77.27%   -0.02%     
- Complexity       59155    59171      +16     
===============================================
  Files             3541     3542       +1     
  Lines           222638   222727      +89     
  Branches         28870    28874       +4     
===============================================
+ Hits            172077   172121      +44     
- Misses           40835    40877      +42     
- Partials          9726     9729       +3     

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