Warning: users are at their own discretion to create .torrent with >= 64 MiB piece size as not
every torrent client supports it.
Larger piece sizes are only available when using libtorrent 2.x. libtorrent 1.x is not
efficient with memory usage and in order to avoid user complaints it is limited to 128 MiB.
Also note that, as of this writing, libtorrent 2.0.9 has an internal limitation that only
allows loading maximum 256 MiB piece size. And therefore > 256 MiB size options are forbidden
for now.
Closes#19527.
PR #19535.
4d2015cfed