Introduce Prometheus metric endpoint replacing Grafana endpoint (#4981)

* Refactor rebase master prometheus_v0.3

* Milestone1: Final Version of v0.3

* no-std or warm compatibility issues, grapana-data -source code reference and correction,applicable

* Cargo.lock paritytech/master rebase

* prometheus networking.rs del, grafana-data-source networking.rs pub edit and note

* chore: reflect various feedback

* Spaces to tabs.

* Replace grafana and tidy

* Add generics

* Add photo back

* Re-fix spaces in primitives/consensus/babe/src/inherents.rs

* Refactor rebase master prometheus_v0.3

* Milestone1: Final Version of v0.3

* no-std or warm compatibility issues, grapana-data -source code reference and correction,applicable

* prometheus networking.rs del, grafana-data-source networking.rs pub edit and note

* chore: reflect various feedback

* Replace grafana and tidy

* Add generics

* Add photo back

* Re-fix spaces in primitives/consensus/babe/src/inherents.rs

* chore: revert this file back to paritytech/master inherents.rs.

* Add newline at EOF

* Tidy

* Use local registry

* fix typo

Co-Authored-By: Max Inden <mail@max-inden.de>

* chore:  Apply review feedback

* endpoint -> exporter

* fix readme

* Remove lazy_static, use ServiceMetrics struct instead

* Switch to using GaugeVecs

* chore: without nightly , edit README

* block_height -> block_height_number

* Switch to a ready_transactions_number gauge

* Update utils/prometheus/src/lib.rs

Co-Authored-By: Max Inden <mail@max-inden.de>

* no-prometheus flag add

* /metrics url Input check

* remove prometheus in Tracing

* remove prometheus in Tracing

* chore: master code rebase edit

* gitlab-check-web-wasm edit code

* From:from and cargo.lock update

* with_prometheus_registry add background_tasks

* utils/prometheus/src/lib.rs: Restructure #[cfg] for wasm without hyper

Given that Hyper is not compatible with WASM targets it needs to be
excluded from WASM builds. Instead of introducing #[cfg] lines
throughout the crate, this patch splits the crate into two: known_os and
unknown_os (WASM).

* utils/prometheus/src/lib.rs: Feature gate known_os module

* client/cli/src/lib.rs: Re-add newline at end of file

Co-authored-by: JeseonLEE <zeroday26@gmail.com>
Co-authored-by: Gavin Wood <github@gavwood.com>
Co-authored-by: Ashley <ashley.ruglys@gmail.com>
Co-authored-by: Hyungsuk Kang <hskang9@gmail.com>

substrate/client/cli/Cargo.toml

@@ -31,6 +31,7 @@ sp-core = { version = "2.0.0", path = "../../primitives/core" }
 sc-service = { version = "0.8", default-features = false, path = "../service" }
 sp-state-machine = { version = "0.8", path = "../../primitives/state-machine" }
 sc-telemetry = { version = "2.0.0", path = "../telemetry" }
+prometheus-exporter = { path = "../../utils/prometheus" }
 sp-keyring = { version = "2.0.0", path = "../../primitives/keyring" }
 names = "0.11.0"
 structopt = "0.3.8"