* Reorg SnapPeerBase descriptor, notably start/stop flags
details:
Instead of using three boolean flags startedFetch, stopped, and
stopThisState a single enum type is used with values SyncRunningOk,
SyncStopRequest, and SyncStopped.
* Restricting snap to eth66 and later
why:
Id-tracked request/response wire protocol can handle overlapped
responses when requests are sent in row.
* Align function names with source code file names
why:
Easier to reconcile when following the implemented logic.
* Update trace logging (want file locations)
why:
The macros previously used hid the relevant file location (when
`chroniclesLineNumbers` turned on.) It rather printed the file
location of the template that was wrapping `trace`.
* Use KeyedQueue table instead of sequence
why:
Quick access, easy configuration as LRU or FIFO with max entries
(currently LRU.)
* Dissolve `SnapPeerEx` object extension into `SnapPeer`
why;
It is logically cleaner and more obvious not to inherit from
`SnapPeerBase` but to specify opaque field object references of the
merged `SnapPeer` object. These can then be locally inherited.
* Dissolve `SnapSyncEx` object extension into `SnapSync`
why;
It is logically cleaner and more obvious not to inherit from
`SnapSyncEx` but to specify opaque field object references of
the `SnapPeer` object. These can then be locally inherited.
Also, in the re-factored code here the interface descriptor
`SnapSyncCtx` inherited `SnapSyncEx` which was sub-optimal (OO
inheritance makes it easier to work with call back functions.)
ba940a5ce7