Fix telemetry span not entering properly & enter span in sc-cli (#7951)

* WIP

* WIP

* Test

* bug fix

* WIP

* Revert "WIP"

This reverts commit 4e51e9adfdf0dc7cf37b562b60a0e83ca1d0b00d.

* doc

* Improve comment on why all spans are preserved

* Added missing suggestion from previous PR

* Use BoxFuture

* Move TelemetrySpan creation to sc-cli, need to test...

* Test code

* Adapt user code

* Revert "Test code"

This reverts commit 333806b2fe1626efaa2691f9f44d0b4dd979bc36.

* Update client/service/src/task_manager/mod.rs

Co-authored-by: David <dvdplm@gmail.com>

* Better & simpler solution

Co-authored-by: David <dvdplm@gmail.com>

substrate/utils/browser/src/lib.rs

@@ -24,7 +24,7 @@ use sc_service::{
 	GenericChainSpec, RuntimeGenesis,
 	KeepBlocks, TransactionStorageMode,
 };
-use sc_telemetry::TelemetryHandle;
+use sc_telemetry::{TelemetryHandle, TelemetrySpan};
 use sc_tracing::logging::LoggerBuilder;
 use wasm_bindgen::prelude::*;
 use futures::{
@@ -72,6 +72,7 @@ where
 		allow_private_ipv4: true,
 		enable_mdns: false,
 	};
+	let telemetry_span = telemetry_handle.as_ref().map(|_| TelemetrySpan::new());
 
 	let config = Configuration {
 		network,
@@ -83,6 +84,7 @@ where
 		}).into(),
 		telemetry_external_transport: Some(transport),
 		telemetry_handle,
+		telemetry_span,
 		role: Role::Light,
 		database: {
 			info!("Opening Indexed DB database '{}'...", name);