[GlobalISel] NFC: Regen some tests + improve test coverage for wide even types

It turns out we don't do an awesome job with weird types like s318 (and other
types near them, like s316).

We don't have any test coverage for those types, so let's add some so it's
easier to see the impact of legalization improvements on them when we make
changes.

Since the test generator was changed, it's easier to update relevant tests prior
to changing things rather than squinting at a bunch of "ah, CHECK is now
CHECK-NEXT" lines. So, let's just regenerate a bunch of tests while we're
here.

Unfortunately the "CHECK-NEXT" scheme doesn't work with legalize-cmp for some
reason, and the test will fail. So keep that one having CHECK lines.