VS Code: improve characters logger (#5855)

This update fixes data discrepancies in calculating the percentage of
code written by Cody events by increasing the accuracy of the
`CharactersLogger`. Previously, the logger was counting character
changes not directly typed by the user. Now, document changes are
grouped by sources, providing flexibility in handling this data as
needed.

The new `cody.characters` telemetry event structure:

```json
{
  "normal_inserted": 0,
  "normal_deleted": 0,
  "undo_inserted": 0,
  "undo_deleted": 0,
  "redo_inserted": 0,
  "redo_deleted": 0,
  "windowNotFocused_inserted": 0,
  "windowNotFocused_deleted": 0,
  "nonVisibleDocument_inserted": 3,
  "nonVisibleDocument_deleted": 0,
  "inactiveSelection_inserted": 0,
  "inactiveSelection_deleted": 0,
  "rapidLargeChange_inserted": 0,
  "rapidLargeChange_deleted": 0
}
```

agent/src/AgentWorkspaceDocuments.ts

@@ -80,7 +80,7 @@ export class AgentWorkspaceDocuments implements vscode_shim.WorkspaceDocuments {
         }
 
         // We have seen this document before, which means we mutate the existing
-        // document to reflect the latest chagnes. For each URI, we keep a
+        // document to reflect the latest changes. For each URI, we keep a
         // singleton document so that `AgentTextDocument.getText()` always
         // reflects the latest value.
         const contentChanges: vscode.TextDocumentContentChangeEvent[] = []