MdeModulePkg/HiiDB: Minimize memory allocation times after ReadyToBoot

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1597

Currently RTData are allocated at/after ReadyToBoot to store the
contents in HiiDatabase and the HII configurations for OS runtime
utilization.
Some platforms may meet S4 resume issue since the allocation after
ReadyToBoot cause memory map change.
Now this patch is to do some overallocation to minimize the number
of memory allocations after ReadyToBoot and also add warning
message when do allocation after ReadyToBoot.

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Signed-off-by: Dandan Bi <dandan.bi@intel.com>
Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>