Move format duration/filesize back into core (#9978)

# Description
Those two commands are very complementary to `into duration` and `into
filesize` when you want to coerce a particular string output.

This keeps the old `format` command with its separate formatting syntax
still in `nu-cmd-extra`.

# User-Facing Changes
`format filesize` is back accessible with the default build. The new
`format duration` command is also available to everybody

# Tests + Formatting

crates/nu-cmd-extra/src/extra/mod.rs

@@ -85,8 +85,6 @@ pub fn add_extra_command_context(mut engine_state: EngineState) -> EngineState {
 
         bind_command!(
             strings::format::Format,
-            strings::format::FileSize,
-            strings::format::FormatDuration,
             strings::encode_decode::EncodeHex,
             strings::encode_decode::DecodeHex,
             strings::str_::case::Str,

crates/nu-cmd-extra/src/extra/strings/format/mod.rs

@@ -1,7 +1,3 @@
 mod command;
-mod duration;
-mod filesize;
 
 pub(crate) use command::Format;
-pub(crate) use duration::FormatDuration;
-pub(crate) use filesize::FileSize;

crates/nu-command/src/default_context.rs

@@ -192,7 +192,9 @@ pub fn add_shell_command_context(mut engine_state: EngineState) -> EngineState {
             StrSubstring,
             StrTrim,
             StrUpcase,
-            FormatDate
+            FormatDate,
+            FormatDuration,
+            FormatFilesize,
         };
 
         // FileSystem

crates/nu-command/src/strings/format/filesize.rs

@@ -19,9 +19,9 @@ impl CmdArgument for Arguments {
 }
 
 #[derive(Clone)]
-pub struct FileSize;
+pub struct FormatFilesize;
 
-impl Command for FileSize {
+impl Command for FormatFilesize {
     fn name(&self) -> &str {
         "format filesize"
     }
@@ -129,6 +129,6 @@ mod tests {
     fn test_examples() {
         use crate::test_examples;
 
-        test_examples(FileSize)
+        test_examples(FormatFilesize)
     }
 }

crates/nu-command/src/strings/format/mod.rs

@@ -1,3 +1,7 @@
 mod date;
+mod duration;
+mod filesize;
 
+pub use self::filesize::FormatFilesize;
 pub use date::FormatDate;
+pub use duration::FormatDuration;

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

@@ -10,7 +10,7 @@ mod str_;
 pub use char_::Char;
 pub use detect_columns::*;
 pub use encode_decode::*;
-pub use format::FormatDate;
+pub use format::*;
 pub use parse::*;
 pub use size::Size;
 pub use split::*;