MdeModulePkg: carve pool pages into the largest chunks possible

MdeModulePkg: carve pool pages into the largest chunks possible

In preparation of the next patch, that serves allocations from higher-up
bins if the current bin is depleted, this patch updates the carving up
strategy to populate the largest bins first. To ensure that there will
always be an allocation of the appropriate size made, the current allocation
request is served first from the newly allocated memory region.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Liming Gao <liming.gao@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17014 6f19259b-4bc3-4df7-8a09-765794883524