Fix sync manager being spawned inited in a separate thread

[delbonis]

To fix a deadlock in a branch that should be merged by the time anyone reads this, some of the init work for the sync manager was moved into a short-lived thread that gets spawned when we start the sync manager tasks. This is the result of some initialization dependency issues around doing genesis and waiting for blocks from L1. This is really screwy and it didn't make sense at the time to do the refactorings in that branch, so I decided to just approve it that way, but it's really not how we should be doing it. Really we want to move some of those genesis duties into the CSM worker and add some extra signalling to do it elegantly and in response to the horizon threshold happening.

Relates to:

• Pull data from CSM state and appropriately create l1 segment #93 (maybe)
• Load Genesis EL data into EL segment in genesis L2 block #106 (maybe)