Bug relates to `early-if-predicator` and `early-ifcvt` passes. If
virtual register has "killed" flag in both basic blocks to be merged
into head, both instructions in head basic block will have "killed" flag
for this register. It makes MIR incorrect.

Example:

```
  bb.0: ; if
    ...
    %0:intregs = COPY $r0
    J2_jumpf %2, %bb.2, implicit-def dead $pc
    J2_jump %bb.1, implicit-def dead $pc

  bb.1: ; if.then
    ...
    S4_storeiri_io killed %0, 0, 1
    J2_jump %bb.3, implicit-def dead $pc

  bb.2: ; if.else
    ...
    S4_storeiri_io killed %0, 0, 1
    J2_jump %bb.3, implicit-def dead $pc
```

After early-if-predicator will become:

```
  bb.0:
    %0:intregs = COPY $r0
    S4_storeirif_io %1, killed %0, 0, 1
    S4_storeirit_io %1, killed %0, 0, 1
```

Having `killed` flag set twice in bb.0 for `%0` is an incorrect MIR.

This reverts commit ff99af7ea03b3be46bec7203bd2b74048d29a52a.

Use nonstatic member instead. This requires explicit conversions, but
many will go away as we continue converting unsigned to Register.

In a few places where it was simple, I changed unsigned to Register.

Support `MachineFunction` in `OptNoneInstrumentation`, also add
`isRequired` to all necessary passes.

This reverts commit 09a4c23eb410d4be52202bed21c967a3653c3544.