add MimirContinuousTestFailingOnWrites and MimirContinuousTestFailing…

[QuantumEnigmaa]

Towards: giantswarm/roadmap#3578

As discussed in the above issue, this PR adds 2 alerts based on the mimir's continous-test component's metrics so that we get alerted when something is wrong in the read or write path.

Those 2 alerts are directly taken from upstream mixins as explained in the comments.

Before merging this PR, I still need to add UTs as well as create a dedicated dashboard for the continous-test component.

Checklist

• Update CHANGELOG.md
• Add Unit tests
• Follow Alert structure
• Consider creating a dashboard (guidelines) (if it does not exist already) to help oncallers monitor the status of the issue.
• Request review from oncall area, as well as team (e.g: oncall-kaas-cloud GitHub group).

[QuentinBisson]

This is not a draft anymore, I repeat, this is not a draft anymore

[hervenicol]

So, we're testing the rate of fails, which is fine.
But the continuous tests also provide a counter of reads and writes. Should we test those as well?

For instance, if we can't write data, we won't get any fails increase. But we also won't get any count of new "continuous test writes", which should probably raise an alert?

[hervenicol]

LGTM.

Note (to self): I'm not happy about the duplicate tests for CAPI. CAPI should now be the default target for tests, and vintage/aws the exception.