qCompress()/qUncompress() cannot handle more than 4GiB of data on Win64

While working on QTBUG-104972, which fixed the most obvious problems with the widening of the functions from 32-bit to 64-bit-sized Qt containers, it turned out that, due to the zlib API using ulong as the size type, 64-bit Windows is unable to handle > 4GiB of (decompressed) data, because sizeof(ulong) is 32-bit on Windows. 64-bit Unix is unaffected, as sizeof(ulong) == 8 there.

To fix, instead of using the compress2() and uncompress() convenience functions, we can use zlib's the stream API (zstream/deflate()/inflate()) directly. Being a stream API, it should not be limited by the size of long.

Acceptance criteria:

1. qCompress() can compress more than 4GiB of data on Windows-64
2. qUncompress() can uncompress more than 4GiB of data on Windows-64
3. functional benchmark for the above two is 64-bit Unix (post QTBUG-104972)
4. the documentation, updated as part of QTBUG-104972, is changed to reflect the removal of the Windows-64 limitation