gui, staking: Implement facilities for mandatory sidestakes and sidestake GUI #2892

Job	Run time
Lint	45s
ARM [GOAL install] [buster]	2m 2s
macOS 12 native [GOAL install] [GUI] [no depends]	9m 9s
Win32	2m 38s
Win64	4m 12s
i386 Linux [GOAL install] [focal]	1m 41s
x86_64 Linux [GOAL install] [GUI] [focal] [no depends]	12m 51s
x86_64 Linux [GOAL install] [GUI] [bionic] [no depends]	12m 59s
macOS 10.14 [GOAL deploy] [GUI] [no tests] [focal]	9m 45s
	56m 2s

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