Transaction committer (service)

[segfault-magnet]

A new component that will continually commit fuel transactions to L1.

To take into account:

• compression (to reduce the size)
• fragmentation (to split transactions across multiple blobs)
• optimizing blob usage -- how long to wait for transactions before submitting the blobs.
• concurrent submissions -- don't wait for one blob to be committed before sending the next one
• to prioritize filling gaps since that blocks block submittal
• retries -- either because of network issues, staleness issues (i.e. squeezed out eqv.), or bumping the price
• resumability -- what happens when the software is restarted
• disaster recovery -- what happens if we loose the db