incus: add completions for remotes and projects

[adamcstephens]

I couldn't find an available list of project config keys to replace the ones from the legacy bash completions. I suspect those were manually entered into that file? This missing available list of all config keys only affects project set as the retrieval of keys can use the existing project's config.

These project configs appear to be only codified here, unless I'm missing something

incus/cmd/incusd/api_project.go

Line 1066 in d4d6c93

projectConfigKeys := map[string]func(value string) error{

[stgraber]

Thanks!