intel/compiler: Update block IPs once per pass

I tested both release builds and debugoptimized builds with dEQP-VK.ssbo.phys.layout.random.16bit.scalar.13. The change to dead_code_eliminate was the bigger win. On a desktop Kabylake system at n=30,

    release build (w/Fedora build flags): -7.79% ± 0.25%
    Meson -Dbuildtype=debugoptimized:     -5.10% ± 0.40%

The change in register_coalesce helped only a tiny bit at n=30,

    release build (w/Fedora build flags): -0.82% ± 0.23%
    Meson -Dbuildtype=debugoptimized:     -0.74% ± 0.27%

The other two commits (marked "FYI") don't help on that test. Those are just the only two other places that use remove a lot.

The difference in the debugoptimized build is the calls to inst_is_in_block(block, this) still exist on each call to remove(). I tried a couple things to reduce that overhead, but I was unsuccessful.

See also #4641 (closed).