tests: split testCreate into smaller tests per installation source type they use
tests: split testCreate into smaller tests per installation source type they use

It has grown over time so much that we could not really make it stable
anymore, since it was failing in different places all the time.

Closes #14069

martinpitt/cockpit,deryni/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit,garrett/cockpit,mvollmer/cockpit,moraleslazaro/cockpit,deryni/cockpit,garrett/cockpit,martinpitt/cockpit,moraleslazaro/cockpit,mvollmer/cockpit,cockpit-project/cockpit,deryni/cockpit,cockpit-project/cockpit,martinpitt/cockpit,moraleslazaro/cockpit,deryni/cockpit,mvollmer/cockpit,garrett/cockpit,garrett/cockpit,mvollmer/cockpit,deryni/cockpit,moraleslazaro/cockpit,martinpitt/cockpit,moraleslazaro/cockpit,mvollmer/cockpit,deryni/cockpit,garrett/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,martinpitt/cockpit,deryni/cockpit,moraleslazaro/cockpit