Take revision submission buffer into account when refilling ephemeral accounts

[peterjan]

Encountered this error on renterd side a lot when trying to fund ephemeral accounts. Turns out the contract is too close to the proof window to be revised, so funding is not possible. I passed down the revisionSubmissionBuffer and return early in refillWorkerAccount.

{"level":"debug","ts":"2024-07-16T16:04:56Z","logger":"autopilot.autopilot.accounts","caller":"autopilot/accounts.go:158","msg":"failed to fund account: couldn't fund account: unable to fetch revision with contract: LatestRevision: ReadResponse: host responded with error: 'internal error'\n","accountID":"ed25519:b3143551b31919df6f23d0f9636ba5d263db0b686a8ebfb787a46e1d47ead5d1","hostKey":"ed25519:da2e16500a5413f31170a37334e91eeccf38af620861991bad21a9e9eb9061e7","balance":"-1807848587969294024770","expected":"1 SC"}

{"level":"warn","ts":1721145896.809674,"logger":"rhp3.LatestRevision","caller":"v3/rhp.go:208","msg":"RPC failed","sessionID":"3092e8db54fc931b","peerAddress":"147.135.54.153:56258","rpcID":"607fe2a089f0c8a0","error":"failed to process payment: failed to process contract payment: failed to lock contract fcid:d86622975ddb3356e29a50cf77342ab813c8f7c5d897d06651d0d8006b437540: contract is not good for modification: contract is too close to the proof window to be revised (479387 > 479382)","elapsed":1.507075184}

[n8maninger]

Was the host responding with internal error? I should change that.