Do not use RhGetCodeTarget in delegate equality (#88611)

Do not use RhGetCodeTarget in delegate equality (#88611)

https://github.com/dotnet/corert/commit/08d78ae391e3eea9ad51265f867e42ee1649282d

The original motivation for this was handling import stubs:
```
Function pointer equality comparison was not handling cross-module pointers correctly when optimizations were enabled
(causes target pointers to be wrapped in jump stubs sometimes). The delegate equality comparison was hitting this bug.
```
We do not have import stubs anymore and unwrapping unboxing stubs serves no purpose here.

Microbenchmarks of delegate equality show ~3x improvement with this change:
```
Bench_DelegateEquality_Positive_OpenStatic<10000000>() took: 355 ms
Bench_DelegateEquality_Positive_ClosedStatic<10000000>() took: 367 ms
Bench_DelegateEquality_Positive_ClosedInstance<10000000>() took: 371 ms

Bench_DelegateEquality_Positive_OpenStatic<10000000>() took: 121 ms
Bench_DelegateEquality_Positive_ClosedStatic<10000000>() took: 120 ms
Bench_DelegateEquality_Positive_ClosedInstance<10000000>() took: 122 ms
```

Additionally, there is some desire to upstream changes for a portable RhGetCodeTarget implementation. Not having to
deal with it at this relatively low-level layer will make things more robust.