* Clarifying/commenting FCU setup condition & small fixes, comments etc.
* Update some logging
* Reorg metrics updater and activation
* Better `async` responsiveness
why:
Block import does not allow `async` task activation while
executing. So allow potential switch after each imported
block (rather than a group of 32 blocks.)
* Handle resuming after previous sync followed by import
why:
In this case the ledger state is more recent than the saved
sync state. So this is considered a pristine sync where any
previous sync state is forgotten.
This fixes some assert thrown because of inconsistent internal
state at some point.
* Provide option for clearing saved beacon sync state before starting syncer
why:
It would resume with the last state otherwise which might be undesired
sometimes.
Without RPC available, the syncer typically stops and terminates with
the canonical head larger than the base/finalised head. The latter one
will be saved as database/ledger state and the canonical head as syncer
target. Resuming syncing here will repeat itself.
So clearing the syncer state can prevent from starting the syncer
unnecessarily avoiding useless actions.
* Allow workers to request syncer shutdown from within
why:
In one-trick-pony mode (after resuming without RPC support) the
syncer can be stopped from within soavoiding unnecessary polling.
In that case, the syncer can (theoretically) be restarted externally
with `startSync()`.
* Terminate beacon sync after a single run target is reached
why:
Stops doing useless polling (typically when there is no RPC available)
* Remove crufty comments
* Tighten state reload condition when resuming
why:
Some pathological case might apply if the syncer is stopped while the
distance between finalised block and head is very large and the FCU
base becomes larger than the locked finalised state.
* Verify that finalised number from CL is at least FCU base number
why:
The FCU base number is determined by the database, non zero if
manually imported. The finalised number is passed via RPC by the CL
node and will increase over time. Unless fully synced, this number
will be pretty low.
On the other hand, the FCU call `forkChoice()` will eventually fail
if the `finalizedHash` argument refers to something outside the
internal chain starting at the FCU base block.
* Remove support for completing interrupted sync without RPC support
why:
Simplifies start/stop logic
* Rmove unused import
ea268e81ff