[VSCode] TypeSpec extension should suggest user to upgrade to GA version if we found user's using preview version

### Clear and concise description of the problem

We always implement the feature of vscode typespec extension with the latest version of TypeSpec.
If user still use the old version of compiler, it is likely to cause unexpected behavior and difficult to trouble shooting.
TypeSpec extension should notify user if the version they currently used does not match the target version of TypeSpec.

Today, it would report nothing if I am using an old version of TypeSpec compiler.

### Checklist

- [x] Follow our [Code of Conduct](https://github.com/microsoft/typespec/blob/main/CODE_OF_CONDUCT.md)
- [x] Read the [docs](https://typespec.io/docs/).
- [x] Check that there isn't already an issue that request the same feature to avoid creating a duplicate.