Node Health warnings (#5951)

* Health endpoint.

* Asynchronous health endpoint.

* Configure time api URL via CLI.

* Tests for TimeChecker.

* Health indication on Status page.

* Adding status indication to tab titles.

* Add status to ParityBar.

* Fixing lints.

* Add health status on SyncWarning.

* Fix health URL for embed.

* Nicer messages.

* Fix tests.

* Fixing JS tests.

* NTP time sync (#5956)

* use NTP to check time drift

* update time module documentation

* replace time_api flag with ntp_server

* fix TimeChecker tests

* fix ntp-server flag usage

* hide status tooltip if there's no message to show

* remove TimeProvider trait

* use Cell in FakeNtp test trait

* share fetch client and ntp client cpu pool

* Add documentation to public method.

* Removing peer count from status.

* Remove unknown upgrade status.

* Send two time requests at the time.

* Revert "Send two time requests at the time."

This reverts commit f7b754b1155076a5a5d8fdafa022801fae324452.

* Defer reporting time synchronization issues.

* Fix tests.

* Fix linting.

parity/cli/config.toml

@@ -78,6 +78,7 @@ disable_periodic = true
 jit = false
 
 [misc]
+ntp_server = "pool.ntp.org:123"
 logging = "own_tx=trace"
 log_file = "/var/log/parity.log"
 color = true

parity/cli/mod.rs

@@ -354,6 +354,8 @@ usage! {
 			or |c: &Config| otry!(c.vm).jit.clone(),
 
 		// -- Miscellaneous Options
+		flag_ntp_server: String = "pool.ntp.org:123",
+			or |c: &Config| otry!(c.misc).ntp_server.clone(),
 		flag_logging: Option<String> = None,
 			or |c: &Config| otry!(c.misc).logging.clone().map(Some),
 		flag_log_file: Option<String> = None,
@@ -590,6 +592,7 @@ struct VM {
 
 #[derive(Default, Debug, PartialEq, Deserialize)]
 struct Misc {
+	ntp_server: Option<String>,
 	logging: Option<String>,
 	log_file: Option<String>,
 	color: Option<bool>,
@@ -890,6 +893,7 @@ mod tests {
 			flag_dapps_apis_all: None,
 
 			// -- Miscellaneous Options
+			flag_ntp_server: "pool.ntp.org:123".into(),
 			flag_version: false,
 			flag_logging: Some("own_tx=trace".into()),
 			flag_log_file: Some("/var/log/parity.log".into()),
@@ -1066,6 +1070,7 @@ mod tests {
 				jit: Some(false),
 			}),
 			misc: Some(Misc {
+				ntp_server: Some("pool.ntp.org:123".into()),
 				logging: Some("own_tx=trace".into()),
 				log_file: Some("/var/log/parity.log".into()),
 				color: Some(true),

parity/cli/usage.txt

@@ -467,6 +467,8 @@ Internal Options:
   --can-restart                    Executable will auto-restart if exiting with 69.
 
 Miscellaneous Options:
+  --ntp-server HOST                NTP server to provide current time (host:port). Used to verify node health.
+                                   (default: {flag_ntp_server})
   -l --logging LOGGING             Specify the logging level. Must conform to the same
                                    format as RUST_LOG. (default: {flag_logging:?})
   --log-file FILENAME              Specify a filename into which logging should be