k12: Refactor

Remove the use of vectors and implement `XofReader`.

Author: aewag

Cargo.lock

@@ -12,7 +12,8 @@ keywords = ["crypto", "hash", "digest"]
 categories = ["cryptography", "no-std"]
 
 [dependencies]
-digest = { version = "0.10.3", features = ["alloc"] }
+digest = { version = "0.10.3", default-features = false, features = ["core-api"] }
+sha3 = "0.10.8"
 
 [dev-dependencies]
 digest = { version = "0.10.3", features = ["alloc", "dev"] }