MemoryBuiltins: remove malloc-family funcs from list

We no longer need specialized knowledge of these allocator functions in
this file since we have the correct attributes available now.

As far as I can tell the changes in the attributor tests are due to
things getting more consistent on alloc-family once we remove the static
list entries.

The two test changes in NewGVN merit extra scrutiny: NewGVN appears to
be _extremely_ sensitive to the inaccessiblememonly for reasons that
are beyond me. As a result, I had-enumerated all the attributes on
allocation functions in those two tests instead of using -inferattrs.
I assumed that the two -disable-simplify-libcalls tests there no
longer are sensible since the function declaration now includes all the
relevant attributes.

Differential Revision: https://reviews.llvm.org/D130107