* Remove CapellaReadiness::NotSynced
Some EEs have a habit of flipping between synced/not-synced, which causes some
spurious "Not read for the merge" messages back before the merge. For the
merge, if the EE wasn't synced the CE simple wouldn't go through the transition
(due to optimistic sync stuff). However, we don't have that hard requirement
for Capella; the CE will go through the fork and just wait for the EE to catch
up. I think that removing `NotSynced` here will avoid false-positives on the
"Not ready logs..". We'll be creating other WARN/ERRO logs if the EE isn't
synced, anyway.
* Change some Capella readiness logging
There's two changes here:
1. Shorten the log messages, for readability.
2. Change the hints.
Connecting a Capella-ready LH to a non-Capella-ready EE gives this log:
```
WARN Not ready for Capella info: The execution endpoint does not appear to support the required engine api methods for Capella: Required Methods Unsupported: engine_getPayloadV2 engine_forkchoiceUpdatedV2 engine_newPayloadV2, service: slot_notifier
```
This variant of error doesn't get a "try updating" style hint, when it's the
one that needs it. This is because we detect the method-not-found reponse from
the EE and return default capabilities, rather than indicating that the request
fails. I think it's fair to say that an EE upgrade is required whenever it
doesn't provide the required methods.
I changed the `ExchangeCapabilitiesFailed` message since that can only happen
when the EE fails to respond with anything other than success or not-found.
d53d43844c