Auto merge of #75382 - JulianKnodt:match_branches, r=oli-obk

Auto merge of #75382 - JulianKnodt:match_branches, r=oli-obk

First iteration of simplify match branches

This is a simple MIR pass that attempts to convert
```
   bb0: {
        StorageLive(_2);
        _3 = discriminant(_1);
        switchInt(move _3) -> [0isize: bb2, otherwise: bb1];
    }

    bb1: {
        _2 = const false;
        goto -> bb3;
    }

    bb2: {
        _2 = const true;
        goto -> bb3;
    }
```
into
```
    bb0: {
        StorageLive(_2);
        _3 = discriminant(_1);
        _2 = _3 == 0;
        goto -> bb3;
    }
```
There are still missing components(like checking if the assignments are bools).
Was hoping that this could get some review though.

Handles #75141

r? @oli-obk