[DRAFT] [inferbo] model std::array::data() and the size of std::array elements

[VladimirMakaev]

Stack: #2193 → #2208 (review only the top commit; lands after #2193)

Inferbo did not model std::array::data() or know the size of std::array elements, so it
missed overruns through data() and reported false positives on memset/memcpy of a whole
std::array, on new/malloc of one, and on std::arrays reached through pointers or
references into C arrays or vectors of them.

#include <array>
#include <cstring>

void f(const char* src) {
  std::array<int, 4> a;
  a.data()[4] = 0; // Infer missed: buffer overrun
  memcpy(a.data(), src, 20); // Infer missed: buffer overrun
  auto* p = new std::array<int, 4>;
  (*p)[3] = 0; // false positive: buffer overrun reported here
  delete p;
}

The std::array type model now records the element size. Pointers to std::array count
std::arrays, using the byte-unit symbols of #2193, and the models of its methods, now including
data(), recount their receiver in elements and keep its offset.

Limitations: std::array fields of local structs are not modelled.

Test plan

New tests in cpp/bufferoverrun/std_array.cpp, with FN_ and FP_ tests for the overruns from
one std::array of a C array into the next, C arrays in a std::array and vectors of
std::arrays. The codetoanalyze tests pass; the example behaves the same with libstdc++.