Add functionality to render pre-existing SARIF files

[vlkl-sap]

Is your feature request related to a problem? Please describe.
I have a recurring use-case where I have a CodeQL database and a SARIF file. The database and the SARIF file originate from another machine (CICD) / another person / etc.

Describe the solution you'd like
I would like the CodeQL extension (which I already have) to offer a way to render such SARIF files similar to results generated from a query in the extension.

Describe alternatives you've considered
I would like not to install yet another extension, esp. since the generic SARIF extension does not work directly with CodeQL databases (yes, I know, I can unpack the source archive, but it's extra steps).

Additional context
N/A

Thanks!