Add include for ai assisted metrics

Related to https://gitlab.com/gitlab-com/gl-infra/reliability/-/issues/24286 we added a metrics catalog definition for ai-assisted services in !6183 (merged)

That MR should have included an include for the newly created file, since they are not picked up automatically. This adds that include.

Running make generate on the previous MR didn't actually generate all of the generated content, because the new file was not being imported. This MR looks like a lot of changes, but the important one is the import 'ai-assisted.jsonnet' line - everything else is generated from that.

The test dashboard is at https://dashboards.gitlab.net/dashboard/snapshot/38VF88JUmdZA1evn6mdlZImDCei17Tqt?orgId=1 but won't have any data until this is merged