refactor(op-devstack): add capability interfaces for polymorphic lookups (Phase 3)

[teddyknox]

This PR introduces capability interfaces for op-devstack that enable polymorphic lookups across component types with different ID signatures. This is Phase 3 of the ID type system refactor.

Problem

Components like RollupBoostNode and OPRBuilderNode provide L2 EL functionality but can't implement L2ELNode because their ID() methods return different types:

// L2ELNode has: ID() L2ELNodeID
// RollupBoostNode has: ID() RollupBoostNodeID
// OPRBuilderNode has: ID() OPRBuilderNodeID

This forced manual multi-registry lookups:

func (o *Orchestrator) GetL2EL(id stack.L2ELNodeID) (L2ELNode, bool) {
    if el, ok := o.l2ELs.Get(id); ok {
        return el, true
    }
    rbID := stack.NewRollupBoostNodeID(id.Key(), id.ChainID())
    if rb, ok := o.rollupBoosts.Get(rbID); ok {
        return rb, true
    }
    // ... check OPRBuilder too
}

Solution

Capability interfaces capture shared behavior without the incompatible ID() method:

type L2ELCapable interface {
    L2EthClient() apis.L2EthClient
    L2EngineClient() apis.EngineClient
    ELNode
}

Polymorphic lookup by key:

sequencer, ok := FindL2ELCapableByKey(registry, "sequencer", chainID)
// Returns whichever L2ELCapable component has that key

Changes

File	Description
stack/capabilities.go	L2ELCapable interface and registry helpers
stack/capabilities_test.go	Comprehensive test suite (9 tests)
Design document	Phase 3 implementation notes

Test Plan

• L2ELCapableKinds() returns expected kinds
• RegistryFindByCapability finds all implementing components
• RegistryFindByCapabilityOnChain filters by chain
• FindL2ELCapableByKey polymorphic lookup works
• FindL2ELCapableByKey prefers L2ELNode when multiple types share a key
• Polymorphic scenario test demonstrates the use case

[ajsutton]

LGTM.

[pcw109550]

The entire files that is added in this PR is dropped at the last PR (phase 6 #18877), and also not used in phase 4, 5. Is this intended, or this specific polymorphic lookup will be addressed in the follow up PR after phase 6?

According to the design doc, FindL2ELCapableByKey should be used at the orchestrator like

func (o *Orchestrator) FindL2EL(key string, chainID eth.ChainID) (L2ELCapable, bool) {
    return stack.FindL2ELCapableByKey(o.registry, key, chainID)
}

Still approving this PR because this comment may be addressed at phase 6, the last PR.

[opgitgovernance]

This pr has been automatically marked as stale and will be closed in 5 days if no updates