feat(mev): add custom mev_type with component-based relay/sidecar/builder resolution

[JasonVranek]

Summary

This adds mev_type: custom, which lets users mix and match relay, sidecar, and builder components arbitrarily without patching Starlark code. Previously, each combination (helix relay + commit-boost, etc.) required a new hardcoded mev_type.

Motivation

My use case requires testing custom Commit-Boost and Helix images against each other (each with custom configs). #1355 allows you to pass a custom CB config but there still are limitations:

1. there's no way to pass a custom config for Helix
2. the mev_type: helix type hardcoded mevboost as the sidecar
3. the mev_type: commit-boost type hardcoded flashbots as the relay

Rather than trying to launch another MEV-Boost that hardcoded my desired combo, I opted to try to generalize to mev_type: custom so that a user can specify their own MEV permutations. Given that Gloas is coming, I also opted to support a mev_type: epbs, which is syntactic sugar over for mev_relay: none, mev_sidecar: none, and mev_builder: buildoor (hopefully useful but this also serves to demo the flexibility of the refactor).

What changed

New: component-based MEV resolution (src/package_io/mev_resolver.star)

mev_type now decomposes into three independent pieces:

• mev_relay — which relay(s) to launch (flashbots, helix, mev-rs, mock, none)
• mev_sidecar — which per-validator PBS service (mev-boost, commit-boost, mev-rs, none)
• mev_builder — which block builder (flashbots, mev-rs, buildoor, mock, none)

Presets (flashbots, helix, commit-boost, etc.) are expanded into components internally and still work exactly as before.

mev_type: custom lets users specify all three explicitly like:

mev_type: custom
mev_params:
    mev_relay: helix
    mev_sidecar: commit-boost
    mev_builder: flashbots

Each component can also override its respective preset default:

mev_type: flashbots
mev_params:
    mev_relay: helix
    mev_sidecar: commit-boost # override just the sidecar
    mev_builder: flashbots

Inline config overrides

Users can now supply full helix_relay_config inline in their Kurtosis YAML. This mimics #1355 but for Helix configs. See .github/tests/mev-custom-helix-cb.yaml as a reference.

Helix launcher cleanup

• Removed the website block from the default helix template and launcher (unused in devnet/CI)
• Added wait="60s" readiness checks on the endpoint (4040) and admin (4050) ports

New: mev_type: epbs preset

Syntactic sugar for ePBS-native block building with no relay infrastructure:

mev_type: epbs

Equivalent to mev_type: custom with mev_relay: none, mev_sidecar: none, mev_builder: buildoor.

Backward compatibility

Existing path	Status
mev_type: flashbots	Unchanged
mev_type: helix	✅ (website removed from template, no functional change to relay)
mev_type: commit-boost	Unchanged
mev_type: mev-rs	Unchanged
mev_type: mock	Unchanged
mev_type: buildoor	Unchanged