[pallet-revive] Add evm feature flag to pallet-revive

[cmichi]

@athei @pgherveou Are you up for putting revm behind a feature flag? If yes, I'd take care of the failing CI.

Since you added the revm dep, 76 more child deps are pulled in for pallet-revive. We are noticing this in ink! with increased build times for anything related to our testing frameworks.

Besides the testing frameworks, the core ink! stuff still has some deps on pallet-revive. We are planning to change that in the future, but the build times for contracts have also increased significantly for the moment.

[athei]

Sorry but no. EVM is not an optional feature. It is just guarded behind a config knob for a very short time until it stabilizes.

Besides the testing frameworks, the core ink! stuff still has some deps on pallet-revive. We are planning to change that in the future, but the build times for contracts have also increased significantly for the moment.

So in the meantime you rather increase the complexity of somebody else codebase? Feature flags are really really really annoying.

[cmichi]

Besides the testing frameworks, the core ink! stuff still has some deps on pallet-revive. We are planning to change that in the future, but the build times for contracts have also increased significantly for the moment.

So in the meantime you rather increase the complexity of somebody else codebase? Feature flags are really really really annoying.

As I wrote, the main issue motivating this PR is with our testing frameworks. Specifically, the ink! E2E testing environment which uses a sandboxed pallet-revive is affected by this overhead. It's not possible for us to remove the pallet-revive dependency for that. This testing environment is used by contract authors, hence there's a direct impact on the devx of users.