[MEV Boost\Builder] Implement builder_status and health check

[StefanBratanov]

PR Description

Tasks:

Retrieve builder status and implement isBuilderAvailable
Track builder flow availability

Changes:

• Introduced ExecutionLayerManager
• Added isBuilderAvailable implementation to ExecutionLayerManager
• Added onSlot logic to ExecutionLayerManager to track and update the builder flow availability

Fixed Issue(s)

related to #5396

Documentation

• I thought about documentation and added the doc-change-required label to this PR if updates are required.

Changelog

• I thought about adding a changelog entry, and added one if I deemed necessary.

[tbenr]

LGTM but I'm still rethinking about this: having the healthcheck in the ExecutionLayerService makes ExecutionLayerChannelImpl unaware of the current status (which makes sense to be aware in case we want to immediately skip to calls based on that)

[StefanBratanov]

LGTM but I'm still rethinking about this: having the healthcheck in the ExecutionLayerService makes ExecutionLayerChannelImpl unaware of the current status (which makes sense to be aware in case we want to immediately skip to calls based on that)

Let me try implementing it in the Impl and see the difference. It should be a quick one.

[tbenr]

But it could be just a peek in the impl.. let's have a quick chat tomorrow if you don't find a quick nice solution

[tbenr]

LGTM