[Master] Desugar field access expression to if statement expression

[rdulmina]

Purpose

$title

Fixes #43769

Approach

Desugared field access expression to the following structure

// Before :
type A {
  B b;
}
type B {
 int c;
}
int? res = a?.b?.c

// After desugar :
any|error temp_result;
temp_result = a;
if temp_result !is error? {
    temp_result = (<A> temp_result).b;
    if temp_result !is error? {
        temp_result = (<B> temp_result).c;
    }
}
int? res = <int> temp_result;
 

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 (master@a6e4f99). Learn more about missing BASE report.
Report is 24 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##             master   #43782   +/-   ##
=========================================
  Coverage          ?   77.39%           
  Complexity        ?    58627           
=========================================
  Files             ?     3446           
  Lines             ?   219260           
  Branches          ?    28981           
=========================================
  Hits              ?   169701           
  Misses            ?    40120           
  Partials          ?     9439           

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[chiranSachintha]

We need to add this changes to 11.x branch as well.