Implement NotifyProjectChanged core signal #2062

Job	Run time
Lint	56s
ARM [GOAL install] [buster]	12m 59s
Win32	14m 55s
macOS 12 native [GOAL install] [GUI] [no depends]	11m 40s
Win64	33m 40s
i386 Linux [GOAL install] [focal]	13m 6s
x86_64 Linux [GOAL install] [GUI] [focal] [no depends]	17m 45s
x86_64 Linux [GOAL install] [GUI] [bionic] [no depends]	16m 25s
x86_64 Linux [ASan] [LSan] [UBSan] [integer] [jammy] [no depends]	19m 38s
macOS 10.14 [GOAL deploy] [GUI] [no tests] [noble]	28m 19s
arm64 macOS 10.14 [GOAL deploy] [GUI] [no tests] [noble]	26m 47s
	3h 16m 10s

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