changes to memory and mutex extraction

[RocaBOT]

There's quite a few things in there, including:

• a (somewhat hacky) way of not printing functions that are part of the go runtime and not the inferred program (in migoinfer/inferer.go and migoinfer/internal/migoinfer/migo.go, mainly) -- this is based on filtering out some keywords and probably doesn't contain some other packages, including the net package that I don't use in my examples
• adding export for (rw)mutex parameters, as well as slight changes to the way their names (and the shared memory ones) are extracted to unify with channel extracted names
• a (somewhat hacky) way to filter memory accesses that are not done to shared variables of the program (those are extracted by us with the mem keyword in their uniqName, so I seach for that to filter out anything not having it)
• slight change to the way mutex and shared variables are handled by migo (needs the update to migo that I will PR as well in a minute)

Obviously, anything in there is up for discussion, especially if we want to keep the output as "pure" as possible, the first hack that filters out non-program functions can be easily reverted, and if you find some of the additions are misplaced I'm happy to know where they would have their better place