Allow secure keypair input for solana-validator cli (#7080)

* Allow secure keypair input for solana-validator cli

* feedback

* Add --skip-mnemonic-validation

* Update --identity to --identity-keypair

* Use struct instead of tuple

* Fix dependencies

* cargo fmt

* Add basic tests

* Use `seed phrase` instead of `mnemonic`

* Update passphrase prompt

clap-utils/src/lib.rs

@@ -19,3 +19,4 @@ macro_rules! version {
 
 pub mod input_parsers;
 pub mod input_validators;
+pub mod keypair;