ci: Use VMs for SanityCheck and CompilerWarnings

ci: Use VMs for SanityCheck and CompilerWarnings

The main reason for this change is to reduce different ways of executing
tasks, making it easier to use custom compute resources for cfbot. A secondary
benefit is that the tasks seem slightly faster this way, apparently the
increased startup overhead is outweighed by reduced runtime overhead.

Reviewed-by: Daniel Gustafsson <[email protected]>
Discussion: https://postgr.es/m/20230808021541[email protected]
Backpatch: 15-, where CI support was added