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/gum/proc-macro/Cargo.toml

@@ -0,0 +1,29 @@
+[package]
+name = "tracing-gum-proc-macro"
+version = "0.9.17"
+authors = ["Parity Technologies <admin@parity.io>"]
+edition = "2021"
+description = "Generate an overseer including builder pattern and message wrapper from a single annotated struct definition."
+
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]
+
+[lib]
+proc-macro = true
+
+[dependencies]
+syn = { version = "1.0.86", features = ["full", "extra-traits"] }
+quote = "1.0.15"
+proc-macro2 = "1.0.36"
+proc-macro-crate = "1.1.3"
+expander = "0.0.6"
+
+[dev-dependencies]
+assert_matches = "1.5.0"
+
+
+[features]
+default = []
+# write the expanded version to a `gum.[a-f0-9]{10}.rs`
+# in the `OUT_DIR` as defined by `cargo` for the `expander` crate.
+expand = []