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>