Decode and Encode hex (#8392)

# Description

I need a command that will transform hex string into bytes and into
other direction.

I've implemented `decode hex` command and `encode hex` command. (Based
on `encode base64` and `decode base64` commands
# User-Facing Changes

```
> '010203' | decode hex
0x[01 02 03]
```

and 

```
> 0x[01 02 0a] | encode hex
'01020A'
```

---------

Co-authored-by: whiteand <andrewbeletskiy@gmail.com>

crates/nu-command/src/strings/encode_decode/decode_hex.rs

@@ -0,0 +1,72 @@
+use super::hex::{operate, ActionType};
+use nu_protocol::ast::Call;
+use nu_protocol::engine::{Command, EngineState, Stack};
+use nu_protocol::{
+    Category, Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Type, Value,
+};
+
+#[derive(Clone)]
+pub struct DecodeHex;
+
+impl Command for DecodeHex {
+    fn name(&self) -> &str {
+        "decode hex"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("decode hex")
+            .input_output_types(vec![(Type::String, Type::Binary)])
+            .vectorizes_over_list(true)
+            .rest(
+                "rest",
+                SyntaxShape::CellPath,
+                "For a data structure input, decode data at the given cell paths",
+            )
+            .category(Category::Formats)
+    }
+
+    fn usage(&self) -> &str {
+        "Hex decode a value."
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Hex decode a value and output as binary",
+                example: "'0102030A0a0B' | decode hex",
+                result: Some(Value::binary(
+                    [0x01, 0x02, 0x03, 0x0A, 0x0A, 0x0B],
+                    Span::test_data(),
+                )),
+            },
+            Example {
+                description: "Whitespaces are allowed to be between hex digits",
+                example: "'01 02  03 0A 0a 0B' | decode hex",
+                result: Some(Value::binary(
+                    [0x01, 0x02, 0x03, 0x0A, 0x0A, 0x0B],
+                    Span::test_data(),
+                )),
+            },
+        ]
+    }
+
+    fn run(
+        &self,
+        engine_state: &EngineState,
+        stack: &mut Stack,
+        call: &Call,
+        input: PipelineData,
+    ) -> Result<PipelineData, ShellError> {
+        operate(ActionType::Decode, engine_state, stack, call, input)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_examples() {
+        crate::test_examples(DecodeHex)
+    }
+}