MdeModulePkg: Fix buffer overflow in MergeMemoryMap #5416

Job	Run time
Analyze (ArmPkg, IA32,X64)	4m 7s
Analyze (CryptoPkg, IA32)	15m 46s
Analyze (CryptoPkg, X64)	16m 16s
Analyze (DynamicTablesPkg, IA32,X64)	7m 37s
Analyze (FatPkg, IA32,X64)	7m 26s
Analyze (FmpDevicePkg, IA32,X64)	7m 31s
Analyze (IntelFsp2Pkg, IA32,X64)	9m 7s
Analyze (IntelFsp2WrapperPkg, IA32,X64)	7m 17s
Analyze (MdeModulePkg, IA32)	15m 53s
Analyze (MdeModulePkg, X64)	16m 7s
Analyze (MdePkg, IA32,X64)	12m 21s
Analyze (PcAtChipsetPkg, IA32,X64)	11m 2s
Analyze (PrmPkg, IA32,X64)	9m 19s
Analyze (SecurityPkg, IA32,X64)	11m 38s
Analyze (ShellPkg, IA32,X64)	12m 59s
Analyze (SourceLevelDebugPkg, IA32,X64)	9m 17s
Analyze (StandaloneMmPkg, IA32,X64)	8m 57s
Analyze (UefiCpuPkg, IA32,X64)	13m 36s
Analyze (UnitTestFrameworkPkg, IA32,X64)	7m 12s
	3h 23m 28s

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