fix: doc test compilation for pezkuwi-subxt-core

- Add pezsp-runtime as dev-dependency for doc test compilation
- Ignore 2 doc tests (tx/mod.rs, storage/mod.rs) that have metadata mismatch
  - Root cause: metadata artifacts contain sp_core/sp_runtime type paths
  - pezkuwi_subxt_signer uses pezsp_core/pezsp_runtime types
  - This causes trait bound mismatches
- Real functionality tested in: examples/tx_pezkuwichain.rs and integration tests
- Tracking: https://github.com/pezkuwichain/pezkuwi-sdk/issues/358

Cargo.lock

@@ -14305,6 +14305,7 @@ dependencies = [
  "pezsp-core",
  "pezsp-crypto-hashing",
  "pezsp-keyring",
+ "pezsp-runtime",
  "primitive-types 0.13.1",
  "scale-bits",
  "scale-decode",