Add troubleshooting steps for the spawning of excessive rg processes

Add troubleshooting steps for the spawning of excessive rg processes.

Users still regularly report the an excessive number of rg (ripgrep) processes are spawned. Looking closely at these reports, almost all of them show rg being executed with the --no-ignore flag. When run with this option, rg searches through directories like node_modules, which drastically increases the execution time. I suspect this happens because users do not understand the meaning of the Use Exclude Setting and Ignore Files button in the VS Code Search UI. With the toggle off, rg is executed with the --no-ignore flag.

Troubleshooting steps should advise users encountering this issue to:

1. Check the toggle button: Ensure that the "Use Exclude Settings and Ignore Files" button is enabled in the Search UI.
2. Verify your ignore settings: Confirm that search.useIgnoreFiles is set to true in your settings.
3. Disable symbolic link following: If the issue persists, setting search.followSymlinks to false may resolve it.
4. Set in settings.json:

{
  "search.exclude": {
    "**/node_modules/**": true,
    ".claude/worktrees/**": true
  }
}

Context:

• https://github.com/microsoft/vscode/issues/193927

• https://github.com/microsoft/vscode/issues/244376

• https://github.com/microsoft/vscode/issues/300132

• https://github.com/microsoft/vscode/issues/305544