[DO NOT MERGE] Encryption At Host Dynamic Validation

[SudoBrendan]

Which issue this PR addresses:

Fixes https://issues.redhat.com/browse/ARO-3837

What this PR does / why we need it:

• Frontend will now validate that Compute Encryption At Host is enabled on customer's subscription before installing clusters that want to use the feature - this will fix a Cluster Install Failure issue
• In memory of Swetha. Thanks for your amazing contributions to our team, I'm glad we can finally get your work across the line with this one.

Test plan for issue:

• Unit tests
• I will perform a manual validation of this, but that will require some effort (a subscription without the feature enabled).

Is there any documentation that needs to be updated for this PR?

N/A fixes a bug

How do you know this will function as expected in production?

Unit tests and manual tests. Since this uses a new First Party Service Principal authorization (GET on Sub features), we should test this out pretty well for Canary as well before moving forward with it to other regions.

[SudoBrendan]

/azp run ci

[SudoBrendan]

/azp run e2e

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[SudoBrendan]

Adding hold because apparently our FPSP permissions were flagged for being not in use for a substantial time, so we need to redo that effort and rollout the permissions before this can merge.