feat: support _meta.pre_function to execute custom logic before execution of each phase #998

Job	Run time
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/http3/admin)	1m 55s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/plugin/[a-k]*)	1m 55s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/plugin/[l-z]*)	1m 57s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/admin t/cli t/config-center-yaml...	1m 56s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/node t/pubsub t/router t/script ...	1m 56s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/http3/admin)	1m 57s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/plugin/[a-k]*)	1m 56s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/plugin/[l-z]*)	1m 56s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/admin t/cli t/config-center-yaml t/cont...	1m 55s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/node t/pubsub t/router t/script t/secre...	1m 56s
	19m 19s

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