Some bridge-related changes

[ImplOfAnImpl]

1. Fix project build when either one or both of "trezor"/"ledger" features are disabled.

   In the bridge I need to be able to build wallet-rpc-client without those features, otherwise it would require the particular versions of parity-scale-codec and ledger-proto that the core uses to be explicitly specified in the bridge as well (and it's not something the bridge should know about). But for consistency I decided to fix it for the entire project, including the case when the entire workspace is built, e.g. cargo build --no-default-features --workspace.

   The end result is not super nice, as I had to add default-features = false to all dependencies that have default = ["trezor", "ledger"] in their [features] - without it the features would be enabled for some of the crates due to cargo's feature unification. E.g. if api-blockchain-scanner-daemon had simply node-comm = { path = "../../wallet/wallet-node-client" }, then during cargo build --no-default-features --workspace both features would be enabled for wallet-node-client, which would propagate them to wallet-types, but other packages, like wallet itself, would still be built without it, producing compilation errors.

   For consistency I also added "trezor"/"ledger" features and default = ["trezor", "ledger"] to test/Cargo.toml (functional tests don't care about those features, but potentially they could).

   But perhaps the better approach would be to remove default = ["trezor", "ledger"] from all libraries and only have it in the apps. Though I'm not sure.

2. In utils/src/fixed_hash.rs the original fixed_hash entities are now exposed via a submodule, so that the bridge doesn't need a direct dependency on fixed_hash.