* Relocate full sync descriptors from global `worker_desc.nim` to local pass
why:
These settings are needed only for the full sync pass.
* Rename `pivotAccountsCoverage*()` => `accountsCoverage*()`
details:
Extract from `worker_desc.nim` into separate source file.
* Relocate snap sync sub-descriptors
details:
..from global `worker_desc.nim` to local pass module `snap_pass_desc.nam`.
* Rename `SnapPivotRef` => `SnapPassPivotRef`
* Mostly removed `SnapPass` prefix from object type names
why:
These objects are solely used on the snap pass.