Revamp Signature Help Feature in LS

[rasika]

Purpose

Revamp Signature Help Feature in LS.

Fixes #4569
Fixes #15818
Fixes #12035

Now Completions also triggers the signature help provider.

Check List

• Read the Contributing Guide
• Required Balo version update
• 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-io]

Codecov Report

❗ No coverage uploaded for pull request base (jballerina@93962c0). Click here to learn what that means.
The diff coverage is 58.03%.

@@              Coverage Diff              @@
##             jballerina   #15874   +/-   ##
=============================================
  Coverage              ?   14.84%           
  Complexity            ?     3763           
=============================================
  Files                 ?     1497           
  Lines                 ?    75716           
  Branches              ?     9917           
=============================================
  Hits                  ?    11242           
  Misses                ?    63064           
  Partials              ?     1410

Impacted Files	Coverage Δ	Complexity Δ
...ng/langserver/completions/util/CompletionUtil.java	0% <ø> (ø)	0 <0> (?)
...etions/builder/BFunctionCompletionItemBuilder.java	0% <0%> (ø)	0 <0> (?)
...nalang/langserver/sourceprune/SourcePruneKeys.java	100% <100%> (ø)	1 <0> (?)
...lang/langserver/sourceprune/LHSTokenTraverser.java	97.29% <100%> (ø)	27 <0> (?)
...lerinalang/langserver/signature/SignatureKeys.java	100% <100%> (ø)	1 <0> (?)
...ang/langserver/signature/SignatureTreeVisitor.java	82.88% <16.66%> (ø)	28 <1> (?)
...lerinalang/langserver/common/utils/CommonUtil.java	13.59% <50%> (ø)	36 <3> (?)
...nalang/langserver/signature/SignatureHelpUtil.java	62.71% <54.69%> (ø)	38 <30> (?)
...alang/langserver/BallerinaTextDocumentService.java	48.18% <69.69%> (ø)	26 <2> (?)
...erinalang/langserver/sourceprune/SourcePruner.java	83.95% <72.72%> (ø)	14 <1> (?)

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[nadeeshaan]

Reviewed