WIP: Add a setting to visually redact enviroment variables (#7124)

Release Notes:

- Added bash syntax highlighting to `.env` files. 
- Added a `private_files` setting for configuring which files should be
considered to contain environment variables or other sensitive
information.
- Added a `redact_private_values` setting to add or remove censor bars
over variable values in files matching the `private_files` patterns.
-(internal) added a new `redactions.scm` query to our language support,
allowing different config file formats to indicate where environment
variable values can be identified in the syntax tree, added this query
to `bash`, `json`, `toml`, and `yaml` files.

---------

Co-authored-by: Nathan <nathan@zed.dev>

crates/copilot/src/copilot.rs

@@ -1251,6 +1251,10 @@ mod tests {
         fn worktree_id(&self) -> usize {
             0
         }
+
+        fn is_private(&self) -> bool {
+            false
+        }
     }
 
     impl language::LocalFile for File {