filter_kubernetes: add kubernetes_namespace metadata #8633

Job	Run time
run-ubuntu-unit-tests (-DFLB_JEMALLOC=On, gcc)	12m 13s
run-ubuntu-unit-tests (-DFLB_JEMALLOC=On, clang)	12m 17s
run-ubuntu-unit-tests (-DFLB_JEMALLOC=Off, gcc)	11m 41s
run-ubuntu-unit-tests (-DFLB_JEMALLOC=Off, clang)	11m 43s
run-ubuntu-unit-tests (-DFLB_SMALL=On, gcc)	11m 44s
run-ubuntu-unit-tests (-DFLB_SMALL=On, clang)	12m 34s
run-ubuntu-unit-tests (-DSANITIZE_ADDRESS=On, gcc)	11m 48s
run-ubuntu-unit-tests (-DSANITIZE_ADDRESS=On, clang)	11m 46s
run-ubuntu-unit-tests (-DSANITIZE_UNDEFINED=On, gcc)	11m 58s
run-ubuntu-unit-tests (-DSANITIZE_UNDEFINED=On, clang)	12m 3s
run-ubuntu-unit-tests (-DFLB_COVERAGE=On, gcc)	43m 8s
run-ubuntu-unit-tests (-DFLB_SANITIZE_MEMORY=On, gcc)	11m 41s
run-ubuntu-unit-tests (-DFLB_SANITIZE_MEMORY=On, clang)	11m 54s
run-ubuntu-unit-tests (-DFLB_SANITIZE_THREAD=On, gcc)	11m 34s
run-ubuntu-unit-tests (-DFLB_SANITIZE_THREAD=On, clang)	11m 51s
run-macos-unit-tests (-DFLB_JEMALLOC=Off)	11m 48s
run-macos-unit-tests (-DFLB_SANITIZE_MEMORY=On)	10m 55s
run-macos-unit-tests (-DFLB_SANITIZE_THREAD=On)	1h 0m 16s
Unit tests (matrix)	1s
	4h 52m 55s

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