Project limits: Use InstanceList

[MggMuggins]

Follow-up to #14315

This tidies up the queries used for project limits checking; it likely results in improved performance for clusters with many entities.

[MggMuggins]

Had a weird error on the CI, unlikely to be related but I'll at least document it here:

=== RUN   TestEndpoints_NetworkSocketBasedActivation
    endpoints_test.go:54: 
        	Error Trace:	/home/runner/work/lxd/lxd/lxd/endpoints/endpoints_test.go:54
        	            				/home/runner/work/lxd/lxd/lxd/endpoints/network_test.go:66
        	Error:      	Received unexpected error:
        	            	readdirnames /tmp/lxd-endpoints-test-1872275927: readdirent lxd-endpoints-test-1872275927: bad file descriptor
        	Test:       	TestEndpoints_NetworkSocketBasedActivation
--- FAIL: TestEndpoints_NetworkSocketBasedActivation (0.00s)

[tomponline]

Error: Failed checking if instance creation allowed: Failed getting usage of project entities: Instance "c1" in project "test-usage" has no "limits.memory" config, either directly or via a profile

[MggMuggins]

InstanceList won't grab profiles that are not in use by any instances. We need all the profiles in the project so that new instances can expand their config/devices.

I've put up a revision here that at least gets us from O(n) queries to O(1) (where n is instances); it does a lot of unnecessary faffing around with profiles that ends up getting thrown out (looks like about 4 queries whose results end up being dropped).

What do you think of something like this?

// lxd/db/projects.go
type ProjectArgs struct {
	Project   api.Project
	Profiles  []api.Profile
	Instances []api.Instance
}

func (c *ClusterTx) ProjectsList(ctx context.Context, filters ...cluster.ProjectFilter) ([]ProjectArgs, error)

I've done a little fiddling here and have about 3/4 an implementation if you'd like me to pursue that further. Otherwise I'll get back to bugs.

[tomponline]

@MggMuggins after the improvements landed in #14315 do you feel this is still worthwhile, are you saying InstanceList is doing unnecessary things all of the time or just in this context?

[MggMuggins]

The changes I've made here go from O(n) queries to O(1) queries for fetchProject; I definitely think this is still worthwhile.

It's inefficient because InstanceList is still doing a couple of queries to get profiles that fetchProject must repeat in order to get all the Project's profiles. In general InstanceList is fine; it's just not quite the right tool for fetchProject.