Register mock instrumentation with PassBuilder and make a run
of pass/analysis checking that corresponding instrumentation calls
are done by pass managers.
(Since I'm new to these unittests) after the overall concept
(as well as details) of my testing approach are confirmed I'm going
to split this change in pieces and attach these pieces to the appropriate
PassInstrumentation patches in my series.
I'm particularly worried about having to use generic EXPECT_CALLs to essentially ignore majority of PassInstrumentation calls. And then InstrumentedPasses subtests perform sequenced checking for a selected subset only.
It does not look very pretty, but it appeared to be the only way to not dive deep into the details of each and every pass manager on each test.