engine: Handle zero size as no limit #8483

Job	Run time
run-ubuntu-unit-tests (-DFLB_JEMALLOC=On, gcc)	12m 9s
run-ubuntu-unit-tests (-DFLB_JEMALLOC=On, clang)	12m 7s
run-ubuntu-unit-tests (-DFLB_JEMALLOC=Off, gcc)	11m 32s
run-ubuntu-unit-tests (-DFLB_JEMALLOC=Off, clang)	11m 38s
run-ubuntu-unit-tests (-DFLB_SMALL=On, gcc)	11m 39s
run-ubuntu-unit-tests (-DFLB_SMALL=On, clang)	12m 56s
run-ubuntu-unit-tests (-DSANITIZE_ADDRESS=On, gcc)	11m 43s
run-ubuntu-unit-tests (-DSANITIZE_ADDRESS=On, clang)	11m 55s
run-ubuntu-unit-tests (-DSANITIZE_UNDEFINED=On, gcc)	11m 45s
run-ubuntu-unit-tests (-DSANITIZE_UNDEFINED=On, clang)	11m 48s
run-ubuntu-unit-tests (-DFLB_COVERAGE=On, gcc)	43m 9s
run-ubuntu-unit-tests (-DFLB_SANITIZE_MEMORY=On, gcc)	11m 31s
run-ubuntu-unit-tests (-DFLB_SANITIZE_MEMORY=On, clang)	11m 30s
run-ubuntu-unit-tests (-DFLB_SANITIZE_THREAD=On, gcc)	11m 36s
run-ubuntu-unit-tests (-DFLB_SANITIZE_THREAD=On, clang)	11m 34s
run-macos-unit-tests (-DFLB_JEMALLOC=Off)	12m 42s
run-macos-unit-tests (-DFLB_SANITIZE_MEMORY=On)	14m 2s
run-macos-unit-tests (-DFLB_SANITIZE_THREAD=On)	11m 15s
Unit tests (matrix)	1s
	4h 6m 32s

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