Feature cleanup (#7182)

Following up on #7180 with some feature cleanup:

- Move the `database` feature from `plugin` to `default`
- Rename the `database` feature to `sqlite`
- Remove `--features=extra` from a lot of scripts etc. 
- No need to specify this, the `extra` feature is now the same as the
default feature set
- Remove the now-redundant 2nd Ubuntu test run

crates/nu-command/src/default_context.rs

@@ -23,7 +23,7 @@ pub fn create_default_context() -> EngineState {
 
         // Database-related
         // Adds all related commands to query databases
-        #[cfg(feature = "database")]
+        #[cfg(feature = "sqlite")]
         add_database_decls(&mut working_set);
 
         // Core