fix(prometheus): disable features when prometheus plugin is turned off #13024

Job	Run time
run ci on centos7 (lua-resty-worker-events, t/plugin/[a-k]*)	35m 0s
run ci on centos7 (lua-resty-worker-events, t/plugin/[l-z]*)	33m 59s
run ci on centos7 (lua-resty-worker-events, t/admin t/cli t/config-center-yaml t/control t/core t...	27m 22s
run ci on centos7 (lua-resty-worker-events, t/node t/pubsub t/router t/script t/secret t/stream-n...	23m 24s
run ci on centos7 (lua-resty-events, t/plugin/[a-k]*)	32m 13s
run ci on centos7 (lua-resty-events, t/plugin/[l-z]*)	33m 53s
run ci on centos7 (lua-resty-events, t/admin t/cli t/config-center-yaml t/control t/core t/debug ...	24m 9s
run ci on centos7 (lua-resty-events, t/node t/pubsub t/router t/script t/secret t/stream-node t/u...	24m 57s
	3h 54m 57s

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