[scudo] Release pages of larger block more frequently

Release pages for large block (size greater than a page) is faster than
the small blocks. Besides, larger blocks are supposed not to be used
so often like smaller blocks which means we may hold several pages used
by large block and rarely get chance to release them if there's no
explicit M_PURGE call. Therefore, relax the release-interval condition
for large block.

This also fixes the assumption that FORCE_ALL should always try page
release.

Differential Revision: https://reviews.llvm.org/D151290