[Gendarme] Update for Mono 3.2

Use Mono.Cecil.Mdb 0.9.5 that is included in Mono 3.2
[Gendarme] Unit tests for #18498
[Gendarme] Fix EnsureLocalDispsable rule (#18498)

We need to keep track of local variables that reference other
variables that hold disposable objects. The rule should not get
triggered if we return one of these local variables. The Mono 3.2
compiler occasionally introduces such local variables.