Summary:
This patch updates the last user of ArgInfo::count and deletes
it. I also delete `GetNumInitArguments()` and `GetInitArgInfo()`.
Classess are callables and `GetArgInfo()` should work on them.
On python 3 it already works, of course. `inspect` is good.
On python 2 we have to add yet another special case. But hey if
python 2 wasn't crufty we wouln't need python 3.
I also delete `is_bound_method` becuase it is unused.
This path is tested in `TestStepScripted.py`
Reviewers: labath, mgorny, JDevlieghere
Reviewed By: labath, JDevlieghere
Subscribers: lldb-commits
Tags: #lldb
Differential Revision: https://reviews.llvm.org/D69742