[llvm] [Pass] Support start/stop in instrumentation (PR #70912)

[via llvm-commits]

paperchalice wrote:

> instead of doing this in the instrumentation, can we do this by not adding the pass to begin with? that seems cleaner.
> 
> e.g. `AddMachinePass` can check if we've added some pass and bail if we have/haven't seen the pass so far

Update for this now. Add a callback to `PassInstrumentationCallbacks` now, `Add*Pass` can decide whether to add pass through this callback.

The work of determining whether a pass is a machine pass will be completed by the pass builder, which requires #76320.

https://github.com/llvm/llvm-project/pull/70912