[LS] Improve loading package listener metadata using a ls-package index

[LakshanWeerasinghe]

Purpose

$subject

Fixes #43172

Approach

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

Samples

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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 53.07443% with 145 lines in your changes missing coverage. Please review.

Project coverage is 77.24%. Comparing base (a72fc91) to head (fa9b234).
Report is 42 commits behind head on master.

Files with missing lines	Patch %	Lines
.../org/ballerinalang/langserver/LSPackageLoader.java	36.79%	65 Missing and 2 partials ⚠️
...ballerinalang/central/client/CentralAPIClient.java	51.94%	32 Missing and 5 partials ⚠️
...oviders/context/util/ServiceTemplateGenerator.java	71.42%	10 Missing and 10 partials ⚠️
...ang/langserver/CentralPackageDescriptorLoader.java	62.50%	9 Missing ⚠️
...in/java/org/wso2/ballerinalang/util/RepoUtils.java	20.00%	4 Missing and 4 partials ⚠️
...rs/imports/AddModuleToBallerinaTomlCodeAction.java	50.00%	0 Missing and 1 partial ⚠️
...lerinalang/langserver/common/utils/CommonUtil.java	66.66%	0 Missing and 1 partial ⚠️
...roviders/context/ImportDeclarationNodeContext.java	83.33%	0 Missing and 1 partial ⚠️
...ns/providers/context/ImportOrgNameNodeContext.java	50.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #43370      +/-   ##
============================================
- Coverage     77.35%   77.24%   -0.11%     
+ Complexity    58588    58563      -25     
============================================
  Files          3460     3460              
  Lines        220086   220062      -24     
  Branches      28909    28940      +31     
============================================
- Hits         170237   169989     -248     
- Misses        40432    40628     +196     
- Partials       9417     9445      +28     

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