Allow to enable ripgrep using an extension setting (disabled by default)

[ggrossetie]

ripgrep can potentially improve performance compared to workspace.findFiles.
However, it has been shown that ripgrep does not behave the same way as findFiles and causes a number of incompatibilities and even performance issues in certain configurations.

Since some users have reported a significant performance improvement using ripgrep, it would be interesting to provide a way to enable this experimental feature. This would also allow us to gather feedback and bug reports in different contexts without forcing users to revert to a previous version in cases where ripgrep does not work as expected.

The setting should clearly state that this feature is experimental and only available on the desktop version.