Use client earlyCapabilities to determine channel join count #1142

Job	Run time
code formatting check	19s
cppcheck	4m 27s
min features with gcc	2m 7s
min features with g++	2m 14s
min features with clang	2m 17s
max features with gcc	3m 22s
max features with g++	2m 33s
max features with clang	4m 2s
max features with clang and AddressSanitized	3m 6s
max features with gcc and DEBUG	2m 14s
max features with gcc for 32-bit arch (legacy OS)	1m 56s
max features with g++ for 32-bit arch (legacy OS)	1m 33s
max features with clang for 32-bit arch (legacy OS)	1m 50s
	32m 0s

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