Replace some of linker_allocator's header includes

The <async_safe/log.h> include in linker_allocator.h was made
unnecessary when the STL dependency was removed.

Replace the linker_*.h header includes with private/bionic_*.h
includes.

This change prepares LinkerMemoryAllocator for use in libc allocating
dynamic ELF TLS memory.

Bug: http://b/78026329
Test: bionic unit tests
Change-Id: I6ad62bd513e71dd3f91a4b724a92b19a1eb6c3b4