[analyzer] Remove IdempotentOperations checker.

This checker has not been updated to work with interprocedural analysis,
and actually contains both logical correctness issues but also
memory bugs.  We can resuscitate it from version control once there
is focused interest in making it a real viable checker again.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@198476 91177308-0d34-0410-b5e6-96231b3b80d8