feat: update mint-repl to use ringct

mint-repl changes:

* enable mint-repl example in Cargo.toml
* rename SpentBook SpentBookNode to match MintNode
* remove DbcUnblinded
* impl reissue_auto command to randomly generate many Dbcs
* remove KeyManager alias for SimpleKeyManager
* remove Signer alias for SimpleSigner
* use RingCtTransaction in place of ReissueTransaction
* disable commands related to multisig usage.
* rework how mint and spentbook nodes are created
* use single char inputs for many user prompts
* support for using SecretKey instead of SecretKeySet
* add newkeys command to generate N new keypairs
* support for ownerless/bearer Dbcs.
* use random decoys from spentbook
* use copy of spentbook code from lib.rs (tests)

Cargo.toml

@@ -85,6 +85,6 @@ termios = "0.3.3"
 # harness = false
 # required-features = [ "dkg" ]
 
-# [[example]]
-# name = "mint-repl"
-# path = "examples/mint-repl/mint-repl.rs"
+[[example]]
+name = "mint-repl"
+path = "examples/mint-repl/mint-repl.rs"