Proposed Changes

• Simplify logic to set up feature tests in preparation for new PeerDAS test updates, and supporting testing multiple features.
• Add docs to FeatureName usage.

Additional Details

Removed previously hard coded EIP7594_* constants, and specify the feature tests at the handler level, this is more flexible, and allows for multiple features to be developed in parallel. For example:

impl<T, E> Handler for SszStaticHandler<T, E>
where
    T: cases::SszStaticType + tree_hash::TreeHash + ssz::Decode + TypeName,
    E: TypeName,
{
    fn is_enabled_for_feature(&self, feature_name: FeatureName) -> bool {
        feature_name == FeatureName::Eip7594
    }
}

When running a test for a feature, tests used to be written this way:

SszStaticHandler::<DataColumnSidecar<MainnetEthSpec>, MainnetEthSpec>::deneb_only()
    .run_for_feature(ForkName::Deneb, FeatureName::Eip7594);

This is quite verbose and may lead to inconsistency between tests. This has been modified to specify the fork at the FeatureName level, so the fork used is only specified once in the feature_name.fork_name() function.

SszStaticHandler::<DataColumnSidecar<MainnetEthSpec>, MainnetEthSpec>::deneb_only()
    .run_for_feature(FeatureName::Eip7594);