Merge GPU and Model "Tested" checkbox into a single checkbox

[mazam-lab]

The GPU and Model dropdowns each have a separate "tested" checkbox. Because our testing was done as a combination of both a particular GPU and a particular Model, when the tested checkbox is turned on, we should ensure that the selected GPU and Model combination is one that we've tested (perhaps do this by restricting the GPU / Model options when the opposite option is filled in?)

[natoscott]

| The GPU and Model dropdowns each have a separate "tested" checkbox.

No, that was never merged to main - it only exists in PR #40 currently.

We need to rethink the idea behind "Tested" and work out how to cater for more than only models and hardware (we also need to prevent recommending configurations that are beyond the saturation level of a given setup - this is quite challenging though).