Alerting: Fix NoRulesSplash being rendered for some seconds, fater creating a rule

[soniaAguilarPeiron]

What is this feature?

This pull request addresses an issue where, just after creating a new alert rule, the alert list view initially renders the message "You have not created alert rules" along with an empty list. However, within a few seconds, the user interface (UI) is updated to correctly display the list of rules.

Context:

This behavior occurs because when a rule is created in the ruler, it immediately appears in the /api/ruler/grafana/api/v1/rules, but there is a slight delay before the rule's status is reflected in /api/prometheus/grafana/api/v1/rules.
The rendering logic for the NoRulesSplash was originally based on the Prometheus rules response, which caused the delay in UI updates.

Why do we need this feature?

The alert list view should display an accurate and up-to-date state of alert rules, immediately after they are created, without any delay or misleading messages.

Who is this feature for?

All users

Special notes for your reviewer:

After the change:

create-first-alert.mp4

Please check that:

• It works as expected from a user's perspective.
• If this is a pre-GA feature, it is behind a feature toggle.
• The docs are updated, and if this is a notable improvement, it's added to our What's New doc.

[VikaCep]

LGTM!

[konrad147]

LGTM!