ARO-14652: Allow the ability to specify custom master/worker VM sizes in release E2E pipeline

[Tof1973]

Which issue this PR addresses:

Fixes ARO-14652

What this PR does / why we need it:

Allow user to specify custom master and/or worker Vm Size instead of default one when creating a cluster through E2E pipeline or hack script.

Test plan for issue:

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

SOP for Testing new instance types (docs/adding-new-instance-types.md) as ben updated to use new variables.

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

I have created cluster following the SOP changes, and we need to run the E2E pipeline with it.

[Tof1973]

E2E pipeline has been run to test with those new parameters here
During the test we have seen:

$ az aro show -n v4-e2e-V113872762-westcentralus-prod -g v4-e2e-V113872762-westcentralus-prod | grep -i vmsize
    "vmSize": "Standard_D8s_v4"
    "vmSize": "Standard_D4s_v4"

ARO-Pipeline changes are implemented in here

[kimorris27]

Kind of a nitpicky request, but I suggested reworking a comment because I'm having trouble understanding what the code directly below it is doing.