[Compiler] Add compiler tests for default functions and function conditions

[SupunS]

Work towards #3773

Description

$subject

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• Targeted PR against master branch
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work
• Code follows the standards mentioned here
• Updated relevant documentation
• Re-reviewed Files changed in the Github PR explorer
• Added appropriate labels

[github-actions]

Cadence Benchstat comparison

This branch with compared with the base branch onflow:feature/compiler commit 2719e99
The command for i in {1..N}; do go test ./... -run=XXX -bench=. -benchmem -shuffle=on; done was used.
Bench tests were run a total of 7 times on each branch.

Collapsed results for better readability

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Please upload report for BASE (feature/compiler@049c7ef). Learn more about missing BASE report.

Additional details and impacted files

@@                 Coverage Diff                 @@
##             feature/compiler    #3788   +/-   ##
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  Coverage                    ?   81.67%           
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  Files                       ?      449           
  Lines                       ?   100329           
  Branches                    ?        0           
===================================================
  Hits                        ?    81941           
  Misses                      ?    15628           
  Partials                    ?     2760           

Flag	Coverage Δ
unittests	81.67% <ø> (?)

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[turbolent]

Nice! The comments help a lot 🙏