Implement GRC::GetAvgNetworkWeight #2048

Job	Run time
ARM [GOAL install] [buster]	3m 52s
Win32	4m 45s
Win64	6m 20s
i386 Linux [GOAL install] [focal]	3m 37s
x86_64 Linux [GOAL install] [GUI] [focal] [no depends]	16m 30s
macOS 12 native [GOAL install] [GUI] [no depends]	10m 15s
x86_64 Linux [GOAL install] [GUI] [bionic] [no depends]	15m 13s
Lint	52s
x86_64 Linux [ASan] [LSan] [UBSan] [integer] [jammy] [no depends]	7m 38s
macOS 10.14 [GOAL deploy] [GUI] [no tests] [noble]	4m 41s
arm64 macOS 10.14 [GOAL deploy] [GUI] [no tests] [noble]	4m 48s
	1h 18m 31s

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