node: remove dependency on wallet backend packages (#23019)
* accounts: new AddBackends method in manager
* node,cmd/geth: mv accman backend init to cmd/geth
* node,cmd/geth: mv scrypt config downstreawm from node
* accounts: use static buffer size for accman sub chan
minor fix
* accounts,cmd/geth: update accman backends through its event loop
* accounts,node: add comments
* accounts: un-export newBackendEvent
* accounts: use chan instead of wg in newBlockEvent
* node: rename isKeyDirEphem
* accounts,cmd: AddBackends->AddBackend
* accounts: fix potential blocking when adding backend
108eec3fee