feat: add the grepSearch tool

[grl-wang]

Problem

required UX for the grep search result

Solution

1. adding the grepSearch tool to support search for text content in files within a directory and its subdirectories.
2. using the vscode-ripgrep npm module to implement the tool: https://github.com/microsoft/vscode-ripgrep
3. tested the tool local E2E, check the following screenshot

License

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[zixlin7]

approved to unblock testing