Deprecate hash base64, extend decode and add encode commands (#5863)

* feat: deprecate `hash base64` command

* feat: extend `decode` and `encode` command families

This commit
- Adds `encode` command family
- Backports `hash base64` features to `encode base64` and `decode base64` subcommands.
- Refactors code a bit and extends tests for encodings
- `decode base64` returns a binary `Value` (that may be decoded into a string using `decode` command)

* feat: add `--binary(-b)` flag to `decode base64`

Default output type is now string, but binary can be requested using this new flag.

crates/nu-command/src/deprecated/hash_base64.rs

@@ -0,0 +1,34 @@
+use nu_protocol::ast::Call;
+use nu_protocol::engine::{Command, EngineState, Stack};
+use nu_protocol::{Category, PipelineData, ShellError, Signature};
+
+#[derive(Clone)]
+pub struct HashBase64;
+
+impl Command for HashBase64 {
+    fn name(&self) -> &str {
+        "hash base64"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build(self.name()).category(Category::Deprecated)
+    }
+
+    fn usage(&self) -> &str {
+        "Deprecated command"
+    }
+
+    fn run(
+        &self,
+        _: &EngineState,
+        _: &mut Stack,
+        call: &Call,
+        _: PipelineData,
+    ) -> Result<PipelineData, ShellError> {
+        Err(nu_protocol::ShellError::DeprecatedCommand(
+            self.name().to_string(),
+            "encode base64".to_owned(),
+            call.head,
+        ))
+    }
+}

crates/nu-command/src/deprecated/mod.rs

@@ -1,3 +1,4 @@
+mod hash_base64;
 mod keep_;
 mod keep_until;
 mod keep_while;
@@ -10,6 +11,7 @@ mod str_find_replace;
 mod str_int;
 mod unalias;
 
+pub use hash_base64::HashBase64;
 pub use keep_::KeepDeprecated;
 pub use keep_until::KeepUntilDeprecated;
 pub use keep_while::KeepWhileDeprecated;