Refactor malloc common into distinct pieces.

The pieces:
- The malloc common shared by static and dynamic code (malloc_common.cpp).
- The code for shared libraries that includes any dlopen'ing
  (malloc_common_dynamic.cpp).
- The implementation of perfetto's heapprofd (malloc_heapprofd.cpp).

This makes it easier to see what's going on in the many different areas.
It should also make it easier to add the allocation capping option.

Other related changes:
- Update the unit tests for android_mallopt. All of the current options
  don't work on static binaries, so make sure that is reflected in the test.
- A few names changes to make sure that all code is consistent.

Test: Ran tests (malloc hooks/malloc debug/perfetto/bionic unit tests).
Change-Id: I0893bfbc0f83d82506fac5d1f37cf92fbdef6f59