* clap-utils: Rename KeypairUrl to SignerSource (cherry picked from commit09dcc9ea04) * clap-utils: Reduce SignerSource's visibility (cherry picked from commitc5ab3ba6f1) * clap-utils: Use `uriparse` crate to parse `SignerSource` (cherry picked from commit5d1ef5d01d) * clap-utils: Add explicit schemes for `ask` and `file` `SignerSource`s (cherry picked from commit6444f0e57b) Co-authored-by: Trent Nelson <trent@solana.com>