Persist produced execution payload envelopes

post-gloas we need to also at least persist payload envelope
(not part of this PR through)

_Originally posted by @twoeths in https://github.com/ChainSafe/lodestar/pull/9595#discussion_r3612453087_

Start by reading PR #9595 and the linked discussion, then trace the post-Gloas path that produces execution payload envelopes. Determine where those envelopes should be persisted and how persistence can be verified. Done means produced payload envelopes are persisted as required by the post-Gloas workflow.

Written by the indexing model from the issue text.