Use solana-cli config keypair in solana-keygen (#8074)

* Use solana-cli config keypair in solana-keygen

* s/infile/keypair for consistency across modules and more generality across access methods

* Move config into separate crate

cli-config/src/lib.rs

@@ -0,0 +1,4 @@
+#[macro_use]
+extern crate lazy_static;
+
+pub mod config;