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/core/chain-selection/src/tree.rs

@@ -140,7 +140,7 @@ fn propagate_viability_update(
 			BlockEntryRef::Explicit(entry) => entry,
 			BlockEntryRef::Hash(hash) => match backend.load_block_entry(&hash)? {
 				None => {
-					tracing::warn!(
+					gum::warn!(
 						target: LOG_TARGET,
 						block_hash = ?hash,
 						"Missing expected block entry"
@@ -360,7 +360,7 @@ fn apply_reversions(
 		let mut ancestor_entry =
 			match load_ancestor(backend, block_hash, block_number, revert_number)? {
 				None => {
-					tracing::warn!(
+					gum::warn!(
 						target: LOG_TARGET,
 						?block_hash,
 						block_number,
@@ -373,7 +373,7 @@ fn apply_reversions(
 					continue
 				},
 				Some(ancestor_entry) => {
-					tracing::info!(
+					gum::info!(
 						target: LOG_TARGET,
 						?block_hash,
 						block_number,
@@ -480,7 +480,7 @@ pub(super) fn finalize_block<'a, B: Backend + 'a>(
 
 			propagate_viability_update(&mut backend, child)?;
 		} else {
-			tracing::debug!(
+			gum::debug!(
 				target: LOG_TARGET,
 				?finalized_hash,
 				finalized_number,
@@ -515,7 +515,7 @@ pub(super) fn approve_block(
 			backend.write_block_entry(entry);
 		}
 	} else {
-		tracing::debug!(
+		gum::debug!(
 			target: LOG_TARGET,
 			block_hash = ?approved_hash,
 			"Missing entry for freshly-approved block. Ignoring"