chore: set resolver v2 at the workspace level

[bishopcheckmate]

Description

Cargo defaults to resolver = "2" in edition 2021 only for singular crates. Workspace tho defaults to the old resolver = "1" and will override this setting for all crates in the workspace. The guideline is to manually set the resolver = "2" on workspace level. This was documented recently and since a few releases produces a warning on building. You don't see it due to the rust-toolchain setting.

Type of change

• [x] Bug fix (non-breaking change which fixes an issue) (not really a bugfix but that's the closest match)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

Contents

• specifies resolver = "2" on workspace level
• removes resolver = "2" from light-client-poc/Cargo.toml because it was ignored anyway

This also fixes this warning:

warning: resolver for the non root package will be ignored, specify resolver at the workspace root:
package:   /data/bishop/zkevm-circuits/light-client-poc/Cargo.toml
workspace: /data/bishop/zkevm-circuits/Cargo.toml

[bishopcheckmate]

I pushed the commit which should fix the builds. With resolver = 2, selected features are not propagated through different dependency types and targets so ethers-solc had to be explicitly enabled in build deps