feat: add InspectorFor trait to enable multi-context EVM factories

[stevencartavia]

Introduces InspectorFor<DB, I>, a new trait that separates factory metadata (EvmFactory) from inspector compatibility. The motivation is unblocking BlockExecutorFactory for multi-context EVM factories like EitherEvm — the current type Context<DB> generic associated type on EvmFactory makes it impossible to express dual inspector bounds (I: Inspector<EthEvmContext<DB>> + Inspector<OpContext<DB>>), which are required by foundry's enum EVM dispatcher. BlockExecutorFactory::create_executor is updated to bound on F::EvmFactory: InspectorFor<&mut State<DB>, I> instead. It makes multi-context EVM factories possible here and is a step toward network-agnostic block execution.

Path forward:

1. alloy-op-evm — mechanical PR: remove type Evm<DB, I> and type Context<DB> GATs, implement InspectorFor<DB, I> where I: Inspector<OpContext<DB>>
2. foundry — implement EitherEvmFactory wrapping existing EVM creation logic, wire TransactionExecutor as BlockExecutorFactory

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes

[mablr]

I think that customizable inspector is required by the current Foundry Evm design. And I haven't found so far any prettier way to do so directly in Foundry.

[mablr]

I guess there's no other way than type erasure to implement Foundry's EitherEvm. The question is whether we're going to keep this pattern.

[figtracer]

it serves as a good bridge for eventually removing it in the future but i think we should keep it now