Subcomponent lifecycle managements

[trianglesphere]

We have several sub-components that exist as go-routines / separate threads. We need to close them on application end, but right now it's not clear which component closes what.

In addition, we don't properly wait for things to be closed:

• L1 Downloader: caching, batching, improved typing, trust-RPC flag #275 (comment)

• optimistic-specs/opnode/rollup/driver/state.go

  Line 150 in 95834ed

  case <-s.done:

  (need to wait for bss to be shut)