multi: utilize cmp package for comparison in Go test files

[mohamedawnallah]

Description

In this PR, we mainly replace reflect.DeepEqual with the cmp package for comparisons in Go test files (*_test.go). The cmp package provides a more powerful and safer alternative for value equality checks.

Closes #20154.

Motivation and Context

As stated in the upstream issue and the cmp documentation:

Package cmp determines equality of values.
This package is intended to be a more powerful and safer alternative to reflect.DeepEqual for comparing whether two values are semantically equal.

The upsteram issue specifically mentioned fullvalue_test.go. However, I think this improvement can be extended to other test files as well.

To facilitate review, this PR includes two commits:

1. The first commit updates fullvalue_test.go.
2. The second commit updates the remaining test files.

This separation allows for easier discussion and review of changes in case we decide to extend it to other test files.

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