feat: support _meta.pre_function to execute custom logic before execution of each phase #927

Job	Run time
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/http3/admin)	2m 22s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/plugin/[a-k]*)	2m 22s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/plugin/[l-z]*)	2m 22s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/admin t/cli t/config-center-yaml...	2m 22s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/node t/pubsub t/router t/script ...	2m 24s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/http3/admin)	2m 22s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/plugin/[a-k]*)	2m 23s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/plugin/[l-z]*)	2m 22s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/admin t/cli t/config-center-yaml t/cont...	2m 22s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/node t/pubsub t/router t/script t/secre...	2m 22s
	23m 43s

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