Update to Rust stable 1.84.1

[athei]

Ref https://github.com/paritytech/ci_cd/issues/1107

We mainly need that so that we can finally compile the pallet_revive fixtures on stable. I did my best to keep the commits focused on one thing to make review easier.

All the changes are needed because rustc introduced more warnings or is more strict about existing ones. Most of the stuff could just be fixed and the commits should be pretty self explanatory. However, there are a few this that are notable:

non_local_definitions

A lot of runtimes to write impl blocks inside functions. This makes sense to reduce the amount of conditional compilation. I guess I could have moved them into a module instead. But I think allowing it here makes sense to avoid the code churn.

unexpected_cfgs

The FRAME macros emit code that references various features like std, runtime-benchmarks or try-runtime. If a create that uses those macros does not have those features we get this warning. Those were mostly when defining a mock runtime. I opted for silencing the warning in this case rather than adding not needed features.

For the benchmarking ui tests I opted for adding the runtime-benchmark feature to the Cargo.toml.

Failing UI test

I am bumping the trybuild version and regenerating the ui tests. The old version seems to be incompatible. This requires us to pass deny_warnings in CARGO_ENCODED_RUSTFLAGS as RUSTFLAGS is ignored in the new version.

Removing toolchain file from the pallet revive fixtures

This is no longer needed since the latest stable will compile them fine using the RUSTC_BOOTSTRAP=1.

[athei]

/cmd prdoc --audience runtime_dev --bump patch

[bkchr]

A lot of runtimes to write impl blocks inside functions. This makes sense to reduce the amount of conditional compilation. I guess I could have moved them into a module instead. But I think allowing it here makes sense to avoid the code churn.

Ser: polkadot-fellows/runtimes@c620a26 🙈

[bkchr]

We should create an issue for this

[athei]

You want to eventually add those features to those crates? Because I thought we just want to allow it forever. Cause the features are essentially useless in those crates. I which you could selectively suppress the warnings.

[bkchr]

The macros should not require these features. For that we have this which enables code, based on features being enabled in the frame-support crate. (The correct way to handle this)

[athei]

A lot of runtimes to write impl blocks inside functions. This makes sense to reduce the amount of conditional compilation. I guess I could have moved them into a module instead. But I think allowing it here makes sense to avoid the code churn.

Ser: polkadot-fellows/runtimes@c620a26 🙈

Ooof. Thank you for your service.