Hide compiler generated branches for try/catch blocks inside async state machine

[matteoerigozzi]

Fixes #465

Improve compiler generated branches detection inside MoveNext() method of async state machine.

This core remove all unexpected branches

[matteoerigozzi]

Last update removes unexpected uncovered line after exception re-thrown inside catch block in the async state machine.

[MarcoRossignoli]

The idea generally is ok to me, we need to be sure that if heuristics fail instrumentation go on, so some more check is not a great problem...I prefer worste perf than fail.
We need much more tests on it.

[MarcoRossignoli]

Please can you attach a full IL source of MoveNext to better review?I'd like to do another review round.

[matteoerigozzi]

@MarcoRossignoli PTAL

I improved the heuristic logic and added several tests to validate it.

[matteoerigozzi]

Attach generated IL for MoveNext() of this example (nested try/catch blocks with conditional exception rethrown)

MoveNext.txt

[MarcoRossignoli]

I'm checking...I need some time, this fix is "articulated", thank's

[MarcoRossignoli]

@matteoerigozzi can you rebase?

[matteoerigozzi]

@MarcoRossignoli rebased!

[MarcoRossignoli]

@matteoerigozzi have you tried to generate a report in release(some nop should disappear so could be good understand if all work as expected) and check if makes sense?

[MarcoRossignoli]

LGTM great job!