[analyzer] Add support for more basic_string API in DanglingInternalBufferChecker.
A pointer referring to the elements of a basic_string may be invalidated
by calling a non-const member function, except operator, at, front,
back, begin, rbegin, end, and rend. The checker now warns if the pointer
is used after such operations.
Differential Revision: https://reviews.llvm.org/D49360