Upgrade controller-runtime to v0.7.0

[stefanprodan]

This PR upgrades the controller-runtime dependency to v0.7.0, fix: #214.

Changes:

• Loggers have been removed from the reconcilers and are now retrieved from the context.Context passed to the Reconcile method and downwards functions.
• Logger configuration flags are now bound to the flag set using BindFlags from runtime/logger, ensuring the same contract across GitOps Toolkit controllers, and the --log-json flag has been deprecated in favour of the --log-encoding=json default.
• The ChangePredicate from runtime has changed to a ReconcilateAtChangedPredicate, and is now chained with the GenerationChangedPredicate from controller-runtime using predicate.Or.
• Signatures that made use of runtime.Object have changed to client.Object, removing the requirement to e.g. call runtime.Object#Object.
• The client.MatchingField function was deprecated, and has been replaced with client.MatchingFields{}.
• The leader-election-role was changed, as leader election now works via the coordination/v1 API.
• The SourceIndexKey constant has been split out into {GitRepository,Bucket}IndexKey constants.
• The util.ObjectKey was added to easily construct a client.ObjectKey / types.NamespacedName from a metav1.Object.

Impersonation changes:

• The impersonation was refactored into KustomizeImpersonation.
• Run GC and health checks using service account impersonation, fix: Support for impersonation when running GC pass #217.

Ref: fluxcd/flux2#613