Use the file keyring backend as a default

[evan-forbes]

In order to simplify keyring use, celestia-node will be using the file keyring backend as a default. In order to stay consistent and avoid possible confusion for users, we should investigate exactly what this entails, and then make a decision on switching the backend here as well.

[rootulp]

Is this issue coupled to the celestia-node implementation of the same? The celestia-node side isn't implemented yet: celestiaorg/celestia-node#603 and https://github.com/celestiaorg/celestia-node/blob/0c2669574fcbc8478cf9572ae5d36c98901916e8/nodebuilder/state/keyring.go#L25

[cmwaters]

Is there a justification anywhere about why file over os? - is it just to simplify things?

[evan-forbes]

cc @renaynay do you remember the exact reason for switching?

[renaynay]

os is wonky on macos cc @evan-forbes @cmwaters