MdeModulePkg: Merge GCD range before convert it to EFI memory

MdeModulePkg: Merge GCD range before convert it to EFI memory

GCD Range is byte address. EFI memory range is page address. To make sure
GCD range is converted to EFI memory range, the following things are added:
1. Merge adjacent GCD range first.
2. Add ASSERT check on GCD range alignment.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Liming Gao <liming.gao@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17813 6f19259b-4bc3-4df7-8a09-765794883524