out_forward: add new 'add_option' configuration property #7946

Job	Run time
run-ubuntu-unit-tests (-DFLB_JEMALLOC=On, gcc)	19m 11s
run-ubuntu-unit-tests (-DFLB_JEMALLOC=On, clang)	19m 53s
run-ubuntu-unit-tests (-DFLB_JEMALLOC=Off, gcc)	17m 48s
run-ubuntu-unit-tests (-DFLB_JEMALLOC=Off, clang)	17m 31s
run-ubuntu-unit-tests (-DFLB_SMALL=On, gcc)	18m 32s
run-ubuntu-unit-tests (-DFLB_SMALL=On, clang)	19m 41s
run-ubuntu-unit-tests (-DSANITIZE_ADDRESS=On, gcc)	18m 33s
run-ubuntu-unit-tests (-DSANITIZE_ADDRESS=On, clang)	17m 57s
run-ubuntu-unit-tests (-DSANITIZE_UNDEFINED=On, gcc)	19m 13s
run-ubuntu-unit-tests (-DSANITIZE_UNDEFINED=On, clang)	18m 57s
run-ubuntu-unit-tests (-DFLB_COVERAGE=On, gcc)	56m 57s
run-ubuntu-unit-tests (-DFLB_SANITIZE_MEMORY=On, gcc)	17m 55s
run-ubuntu-unit-tests (-DFLB_SANITIZE_MEMORY=On, clang)	17m 32s
run-ubuntu-unit-tests (-DFLB_SANITIZE_THREAD=On, gcc)	18m 33s
run-ubuntu-unit-tests (-DFLB_SANITIZE_THREAD=On, clang)	17m 33s
run-macos-unit-tests (-DFLB_JEMALLOC=Off)	13m 29s
run-macos-unit-tests (-DFLB_SANITIZE_MEMORY=On)	15m 30s
run-macos-unit-tests (-DFLB_SANITIZE_THREAD=On)	14m 2s
Unit tests (matrix)	1s
	5h 58m 48s

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