Allow use of oracle keys stored in places other than "os"

[Matthews3301]

In terra configuration, it's possible to store keys in one of the following keyring backends:
os|file|kwallet|pass|test|memory

It would be great if it was possible to pass this parameter to the oracle alongside key name, e.g.
terra-oracle service --from={name_of_feeder} --from-keyring={os|file|kwallet|pass|test|memory} --broadcast-mode=block --config={path_to_config.toml} --vote-mode aggregate

This is equivalent of --keyring-backend flag in terrad