Add target endpoint to `CommissioningWindowOpener` #101014

Job	Run time
Build on Darwin (clang, python_lib, simulated)	1h 20m 4s
Build on Linux (fake, gcc_release, clang, simulated)	2h 9m 56s
Build on Linux (coverage)	19m 52s
Build on Linux (gcc_debug)	1h 9m 52s
Build on Linux (python_lib)	29m 58s
Build on Linux (python lighting-app)	10m 56s
	5h 40m 38s

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