This is the subset of incremental tests that should continue to use `bpass`
even after `cpass` is supported, because they (presumably) involve codegen.
Long ago, UI tests were divided into "compile" and "run" tests. Later, the
compile tests were further subdivided into "check" and "build" tests, to speed
up tests that don't need a full build.
The same split was never applied to incremental test revisions, so the only way
to perform a check build in incremental tests is (confusingly) to use a `cfail`
revision and then specify `//@ check-fail` or `//@ check-pass`.
This PR makes room for dedicated check-fail and check-pass revisions by
renaming the existing `cfail` and `cpass` revisions to `bfail` and `bpass`,
since they currently perform a full build.
Zalathar