This patch contains several changes to `deallocate_size.pass.cpp`:
1. `static_cast`-ing some parameters to `size_t` to avoid narrowing.
2. Changing the type of loop variable `i` to `unsigned int` avoid
signedness mismatch with the constructor parameter.
3. Separately counting allocations and deallocations in variables
`allocated_` and `deallocated_`, and changing their type to `uint64_t`.
4. Avoiding `assert`-ing count of allocations when a `basic_string` is
allocated, just `assert`-ing after destruction instead.

Making it meet the requirements for allocator since C++11. Fixes
#113609.

This PR doesn't make it meet the C++03 allocator requirements, because
that would make the type too verbose and libc++ has backported many
C++11 features to the C++03 mode.

Drive-by: Removes the `TEST_CONSTEXPR_CXX14` on `allocate`/`dealocate`
which is never in effect (and causes IFNDR-ness before C++23), since
these functions modify the namespace-scoped variable `allocated_`.

This is regression test for #90292.

Allocator used in test is very similar to test_allocator.
However, reproducer requires size_type of the string
to be 64bit, but test_allocator uses 32bit.

32bit size_type makes `sizeof(string::__long)` to be 16,
but the alignment issue fixed with #90292 is only triggered
with default `sizeof(string::__long)` which is 24.

Fixes #92128.

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Co-authored-by: Louis Dionne <ldionne.2@gmail.com>