Set version to 2.3.0-rc2 #4215

Job	Run time
dependencies (linux, gcc, Debug)	3m 19s
dependencies (linux, gcc, Release)	2m 15s
dependencies (linux, clang, Debug)	2m 57s
dependencies (linux, clang, Release)	2m 15s
coverage (linux, gcc, Debug)	13m 12s
conan	2m 53s
test (linux, gcc, Debug)	11m 17s
test (linux, gcc, Debug, -Dunity=ON)	7m 56s
test (linux, gcc, Release)	12m 5s
test (linux, gcc, Release, -Dunity=ON)	8m 14s
test (linux, clang, Debug)	9m 29s
test (linux, clang, Debug, -Dunity=ON)	6m 18s
test (linux, clang, Release)	11m 5s
test (linux, clang, Release, -Dunity=ON)	8m 14s
	1h 41m 29s

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