chore(AlertRuleGroup): Remove unnecessary requests during reconcile

[Baarsgaard]

Background

Noticed that the AlertRuleGroup reconciler would send 1 request per rule in the spec and thought it was a bit excessive.

It turns out that you can update all rules in a group at once by just updating the group, and if a rule is omitted from the update, it is then deleted.

But to create a rule, it is necessary to send POST for each new rule.
Knowing that, it was simple to just find the missing rules on a given instance and do the minimum GET and PUT requests to reconcile the difference.

Implementation

I would have liked to make smaller commits, but making individual commits that compiled and worked could not really be done easily.

• The conversion to a Grafana compatible model has pulled out of the reconcile loop and is now done before any requests are made.
• Existing rules are now updated at once with a PUT request on the group.
• Deleted rules are removed in the same PUT request
• New rules are created individually if missing on the remote instance
• Provenance header is now always included, editable is still immutable and requires a recreate.
• The array of rules now has a MinItems=1 requiring at least one rule to be defined.
  In the old implementation this would apply successfully but do nothing?

Number of requests sent to each Grafana instance during a reconcile*.

Scenario	Before	Now
New AlertRuleGroup created	N+2	N+2
No changes	N+2	2
1 new rule	N+2	ΔN+2 = 1+2
2 new rules	N+2	ΔN+2 = 2+2
1 Deleted rule	N+1+2	2
2 Deleted rules	N+2+2	2

N = number of rules in a group

*multiply by the number of instances for the total number of requests

I would appreciate individual testing as this is almost a rewrite of the reconcile function with a lot of changes.