Add support for Confidential VMs and Trusted launch for VMs

[mresvanis]

/kind feature

Describe the solution you'd like
I would like to be able to spawn Azure Confidential VMs and to enabled Trusted launch for VMs.

Confidential VMs provide protection to data-in-use by encryption the VM memory with keys that Azure doesn't have access to. Those VMs can also be attested by the user.

See Azure Confidential Computing for more details.

Trusted launch for VMs provide SecureBoot and vTPM attestation.

Anything else you would like to add:
Confidential VMs require specific OS images.
Trusted launch for VMs include these limitations.

Environment:

• cluster-api-provider-azure version:
• Kubernetes version: (use kubectl version):
• OS (e.g. from /etc/os-release):

[nojnhuh]

/assign @mresvanis

Assigning this since you've started working on this in the PR. Thanks!