feat: push prometheus metrics to pushgateway on-demand #1461

Job	Run time
Cross checking x86_64-pc-windows-msvc on stable	2m 31s
Cross checking x86_64-pc-windows-gnu on stable	3m 59s
Cross checking x86_64-apple-darwin on stable	12m 50s
Cross checking aarch64-apple-darwin on stable	4m 20s
Cross checking x86_64-unknown-linux-gnu on stable	4m 50s
Cross checking x86_64-unknown-linux-musl on stable	5m 3s
Cross checking aarch64-unknown-linux-gnu on stable	53s
Cross checking aarch64-unknown-linux-musl on stable	52s
Cross checking i686-unknown-linux-gnu on stable	1m 10s
Cross checking x86_64-unknown-netbsd on stable	51s
Cross checking armv7-unknown-linux-gnueabihf on stable	48s
Result (Cross-CI)	1s
	38m 8s

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