feat: Make failure policy configurable

[mikebryant]

What does this PR do?

Make the admission controller failure policy configurable

Motivation

Keep having the datadog agents fail to mutate things during disruption

Fixes #8475

Additional Notes

Starting looking at adding a test, got stuck due to:

Running tool: /usr/local/bin/go test -timeout 30s -run ^TestGenerateTemplatesV1$

package github.com/DataDog/datadog-agent/pkg/clusteragent/admission/controllers/webhook: build constraints exclude all Go files in /Users/mikebryant/go/src/github.com/DataDog/datadog-agent/pkg/clusteragent/admission/controllers/webhook

Describe how to test your changes

Not done yet. Providing a work in progress in the hope someone else can help finish this

Write here in detail how you have tested your changes
and instructions on how this should be tested in QA.

Describe or link instructions to set up environment
for testing, if the process requires more than just
running the agent on one of the supported platforms.

Checklist

• A release note has been added or the changelog/no-changelog label has been applied.
• The need-change/operator and need-change/helm labels has been applied if applicable.
• The appropriate team/.. label has been applied, if known.
• If known, an appropriate milestone has been selected; otherwise the Triage milestone is set.
• The config template has been updated if applicable.

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