Expose metadata-hash feature from polkadot crate (#4886)

Enabling this feature when building the `polkadot ` crate will lead it
to being enabled for the builtin westend and rococo runtimes. The result
of that is that a merkleized metadata hash will be computed (at some
time cost) in those runtimes, which will allow transactions which
include a hash via the `CheckMetadataHash` extension to work.

The idea is that this is useful for being able to test/experiment with
the `CheckMetadataHash` extension against local nodes.

---------

Co-authored-by: command-bot <>
Co-authored-by: Bastian Köcher <git@kchr.de>

Author: jsdw

Cargo.lock

@@ -68,6 +68,11 @@ jemalloc-allocator = [
 	"polkadot-overseer/jemalloc-allocator",
 ]
 
+# Generate the metadata hash needed for CheckMetadataHash
+# in the builtin test runtimes (westend and rococo).
+metadata-hash = [
+	"polkadot-cli/metadata-hash",
+]
 
 # Enables timeout-based tests supposed to be run only in CI environment as they may be flaky
 # when run locally depending on system load

polkadot/Cargo.toml

@@ -49,6 +49,7 @@ substrate-build-script-utils = { workspace = true, default-features = true }
 [features]
 default = ["cli", "db", "full-node"]
 db = ["polkadot-service/db"]
+metadata-hash = ["polkadot-service/metadata-hash"]
 service = ["dep:polkadot-service"]
 cli = [
 	"clap",

polkadot/cli/Cargo.toml

@@ -201,6 +201,13 @@ rococo-native = [
 	"rococo-runtime-constants",
 ]
 
+# Generate the metadata hash needed for CheckMetadataHash
+# in the test runtimes.
+metadata-hash = [
+	"rococo-runtime?/metadata-hash",
+	"westend-runtime?/metadata-hash",
+]
+
 runtime-benchmarks = [
 	"frame-benchmarking-cli/runtime-benchmarks",
 	"frame-benchmarking/runtime-benchmarks",