libstdc++: Fix src/c++17/memory_resource for H8 targets [PR107801]

libstdc++: Fix src/c++17/memory_resource for H8 targets [PR107801]

This fixes compilation failures for H8 multilibs. For the normal
multilib (ILP16L32?), the chunk struct does not have the expected size,
because uint32_t is type long and has alignment 4 (by default). This
forces sizeof(chunk) to be 12 instead of the expected 10. We can fix
that by using bitset::size_type instead of uint32_t, so that we only use
a 16-bit size when size_t and pointers are 16-bit types.

For the I32LP16 multilibs that use -mint32 int is wider than size_t
and so arithmetic expressions involving size_t promote to int. This
means we need some explicit casts back to size_t.

libstdc++-v3/ChangeLog:

	PR libstdc++/107801
	* src/c++17/memory_resource.cc (chunk::_M_bytes): Change type
	from uint32_t to bitset::size_type. Adjust static assertion.
	(__pool_resource::_Pool::replenish): Cast to size_t after
	multiplication instead of before.
	(__pool_resource::_M_alloc_pools): Ensure both arguments to
	std::max have type size_t.