observability: tracing gum, automatically cross ref traceID (#5079)

* add some gum

* bump expander

* gum

* fix all remaining issues

* last fixup

* Update node/gum/proc-macro/src/lib.rs

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* change

* netowrk

* fixins

* chore

* allow optional fmt str + args, prep for expr as kv field

* tracing -> gum rename fallout

* restrict further

* allow multiple levels of field accesses

* another round of docs and a slip of the pen

* update ADR

* fixup lock fiel

* use target: instead of target=

* minors

* fix

* chore

* Update node/gum/README.md

Co-authored-by: Andrei Sandu <54316454+sandreim@users.noreply.github.com>

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>
Co-authored-by: Andrei Sandu <54316454+sandreim@users.noreply.github.com>

polkadot/node/network/availability-distribution/src/requester/mod.rs

@@ -103,7 +103,7 @@ impl Requester {
 	where
 		Context: SubsystemContext,
 	{
-		tracing::trace!(target: LOG_TARGET, ?update, "Update fetching heads");
+		gum::trace!(target: LOG_TARGET, ?update, "Update fetching heads");
 		let ActiveLeavesUpdate { activated, deactivated } = update;
 		// Stale leaves happen after a reversion - we don't want to re-run availability there.
 		if let Some(leaf) = activated.filter(|leaf| leaf.status == LeafStatus::Fresh) {
@@ -140,7 +140,7 @@ impl Requester {
 		// Also spawn or bump tasks for candidates in ancestry in the same session.
 		for hash in std::iter::once(leaf).chain(ancestors_in_session) {
 			let cores = get_occupied_cores(ctx, hash).await?;
-			tracing::trace!(
+			gum::trace!(
 				target: LOG_TARGET,
 				occupied_cores = ?cores,
 				"Query occupied core"
@@ -212,7 +212,7 @@ impl Requester {
 						)
 						.await
 						.map_err(|err| {
-							tracing::warn!(
+							gum::warn!(
 								target: LOG_TARGET,
 								error = ?err,
 								"Failed to spawn a fetch task"