[GlobalISel] Combine icmp eq/ne x, 0/1 -> x when x == 0 or 1

This adds the following combines:

```
x = ... 0 or 1
c = icmp eq x, 1

->

c = x
```

and

```
x = ... 0 or 1
c = icmp ne x, 0

->

c = x
```

When the target's true value for the relevant types is 1.

This showed up in the following situation:

https://godbolt.org/z/M5jKexWTW

SDAG currently supports the `ne` case, but not the `eq` case. This can probably
be further generalized, but I don't feel like thinking that hard right now.

This gives some minor code size improvements across the board on CTMark at
-Os for AArch64. (0.1% for 7zip and pairlocalalign in particular.)

Differential Revision: https://reviews.llvm.org/D109130