REFACTOR: move source out of deprecated commands (#9060)

# Description
the plan of deprecating `source` never really came to conclusion, so i
propose to move it out of the deprecated commands in this PR.
i've moved it to `nu-command::misc`, which can be changed 👍 

# User-Facing Changes
```
$nothing
```

# Tests + Formatting
- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- ⚫ `toolkit test`
- ⚫ `toolkit test stdlib`

# After Submitting
```
$nothing
```

crates/nu-command/src/default_context.rs

@@ -103,6 +103,7 @@ pub fn create_default_context() -> EngineState {
 
         // Misc
         bind_command! {
+            Source,
             Tutor,
         };
 
@@ -443,7 +444,6 @@ pub fn create_default_context() -> EngineState {
             MathEvalDeprecated,
             OldAlias,
             RPadDeprecated,
-            Source,
             StrCollectDeprecated,
             StrDatetimeDeprecated,
             StrDecimalDeprecated,

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

@@ -6,7 +6,6 @@ mod lpad;
 mod math_eval;
 mod old_alias;
 mod rpad;
-mod source;
 mod str_datetime;
 mod str_decimal;
 mod str_find_replace;
@@ -20,7 +19,6 @@ pub use lpad::LPadDeprecated;
 pub use math_eval::SubCommand as MathEvalDeprecated;
 pub use old_alias::OldAlias;
 pub use rpad::RPadDeprecated;
-pub use source::Source;
 pub use str_datetime::StrDatetimeDeprecated;
 pub use str_decimal::StrDecimalDeprecated;
 pub use str_find_replace::StrFindReplaceDeprecated;

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

@@ -1,3 +1,5 @@
+mod source;
 mod tutor;
 
+pub use source::Source;
 pub use tutor::Tutor;