box: fix SIGSEGV on unaligned access to a struct with extended alignment

All structures with a non-default alignment (set by `alignas()`) must be
allocated by `aligned_alloc()`, otherwise an access to such a structure
member fill crash, e.g. if compiled with AVX-512 support.

Closes #10215
Part of #10631

NO_DOC=bugfix
NO_TEST=tested by debug_asan_clang workflow
NO_CHANGELOG=fix is actually not user-visible, because tarantool still
             doesn't work with enabled AVX-512 (#10671)

(cherry picked from commit a60ec82d4f07720148b0724e5feff31f76291b56)