refactor(gas_limiter): canonical + overlay design with epoch tag

[julio4]

Refactor the per-address gas/compute limiter to use per-payload overlays over a shared canonical limiter.

Each payload job now records limiter usage in its own overlay and commits it back when the job finishes. This keeps in-flight payload builds isolated while preserving persistent sender debt across jobs. The
limiter also rejects stale overlay commits when the canonical state has already advanced.

Changes

• Add canonical + overlay limiter model for gas and compute buckets.
• Add epoch checks to prevent stale overlays from committing.
• Add checkpoint/restore support for rolling back failed tx attempts.
• Wire payload jobs to use limiter overlays.
• Refresh limiter state before forking payload overlays.

[akundaz]

This conflicts hugely with my existing PR (#487). Can you describe to me

• the api you need for continuous building
• and the performance concerns you have

Then we can build on top of each other and streamline the work properly

[julio4]

This conflicts hugely with my existing PR (#487). Can you describe to me

• the api you need for continuous building
• and the performance concerns you have

Then we can build on top of each other and streamline the work properly

Yes that's why I extracted it from continuous PR, so that we can merge it first and we can update 487 with this foundation.

There's detailed "What was missing" and "What this fixes for continuous mode" sections in the description upper, but tldr we need cheap copy/overlay as only the winning candidate should consume budgets.

[akundaz]

Looks much better thank you! Just get CI passing and I think this should be good to go