User story: 

As a PMM admin user, I need to be able to see the list of Alert Rules so that list can be used to run actions or review the Alerts Rules.

This is the main screen for users to work with Integrated Alerting. Here they'll see and add/edit Alert rules, so they'll get notifications later when something is broken. 

The MVP implementation is the minimal one.  

Acceptance Criteria:

• The user is seeing the message `No alert rules found` when the recordset is empty.

• The columns presented according to data from Alert Rule creation 

• As a User I'm able to see which alert rules are currently firing (the `Last Notified` column must display a colored circle corresponding to one of four alert states, i.e.: Critical, High, Warning, Info)

• the value in the Last notified columns leads to an Alerts list page ( PMM-6994 )  

Implementation details:

• code and PRs get pushed to percona-platform/grafana repository

• test coverage

• honor light/dark mode

Out of scope for this issue:

• any sorting

• pagination

• top filtering