[Compiler] Support accessing result variable inside post conditions

[SupunS]

Work towards #3742

Description

result variable gets passed as a parameter (last parameter) to the generated functions (for conditions).
e.g:

struct interface A {
    access(all) view fun $A.test.postConditions(_ a1: T1, _ a2: T2, _ result: T3): Void {
        ...
    }
}

---

• 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 17bfacc
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

[turbolent]

Nice!