Change the usage misnomer to "description" (#13598)

# Description
    
The meaning of the word usage is specific to describing how a command
function is *used* and not a synonym for general description. Usage can
be used to describe the SYNOPSIS or EXAMPLES sections of a man page
where the permitted argument combinations are shown or example *uses*
are given.
Let's not confuse people and call it what it is a description.

Our `help` command already creates its own *Usage* section based on the
available arguments and doesn't refer to the description with usage.

# User-Facing Changes

`help commands` and `scope commands` will now use `description` or
`extra_description`
`usage`-> `description`
`extra_usage` -> `extra_description`

Breaking change in the plugin protocol:

In the signature record communicated with the engine.
`usage`-> `description`
`extra_usage` -> `extra_description`

The same rename also takes place for the methods on
`SimplePluginCommand` and `PluginCommand`

# Tests + Formatting
- Updated plugin protocol specific changes
# After Submitting
- [ ] update plugin protocol doc

crates/nu-command/src/stor/create.rs

@@ -28,7 +28,7 @@ impl Command for StorCreate {
             .category(Category::Database)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Create a table in the in-memory sqlite database."
     }
 

crates/nu-command/src/stor/delete.rs

@@ -29,7 +29,7 @@ impl Command for StorDelete {
             .category(Category::Database)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Delete a table or specified rows in the in-memory sqlite database."
     }
 

crates/nu-command/src/stor/export.rs

@@ -23,7 +23,7 @@ impl Command for StorExport {
             .category(Category::Database)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Export the in-memory sqlite database to a sqlite database file."
     }
 

crates/nu-command/src/stor/import.rs

@@ -23,7 +23,7 @@ impl Command for StorImport {
             .category(Category::Database)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Import a sqlite database file into the in-memory sqlite database."
     }
 

crates/nu-command/src/stor/insert.rs

@@ -33,7 +33,7 @@ impl Command for StorInsert {
             .category(Category::Database)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Insert information into a specified table in the in-memory sqlite database."
     }
 

crates/nu-command/src/stor/open.rs

@@ -20,7 +20,7 @@ impl Command for StorOpen {
             .category(Category::Database)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Opens the in-memory sqlite database."
     }
 

crates/nu-command/src/stor/reset.rs

@@ -17,7 +17,7 @@ impl Command for StorReset {
             .category(Category::Database)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Reset the in-memory database by dropping all tables."
     }
 

crates/nu-command/src/stor/stor_.rs

@@ -14,11 +14,11 @@ impl Command for Stor {
             .input_output_types(vec![(Type::Nothing, Type::String)])
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Various commands for working with the in-memory sqlite database."
     }
 
-    fn extra_usage(&self) -> &str {
+    fn extra_description(&self) -> &str {
         "You must use one of the following subcommands. Using this command as-is will only produce this help message."
     }
 

crates/nu-command/src/stor/update.rs

@@ -38,7 +38,7 @@ impl Command for StorUpdate {
             .category(Category::Database)
     }
 
-    fn usage(&self) -> &str {
+    fn description(&self) -> &str {
         "Update information in a specified table in the in-memory sqlite database."
     }