Replaces go-autorest MS graph client with msgraph-sdk-go

[austingebauer]

Overview

This PR replaces the deprecated go-autorest module with msgraph-sdk-go. Additionally, it migrates the azure-sdk-for-go to the new package structure (see related issue).

There are no known API changes or compatibility breaks in this PR.

Testing

All tests in the repository are passing. Additionally, I manually tested the secrets engine functionality using our Terraform bootstrap which pulls an IMDS token off of a VM.

I've additionally added an acceptance test that actually uses Azure resources to login in.

Related Issues/Pull Requests

• deprecated packages from github.com/Azure/azure-sdk-for-go have been removed vault-plugin-secrets-azure#143

Contributor Checklist

• Add output for any tests not ran in CI to the PR description (eg, acceptance tests)
• Backwards compatible

[raymonstah]

Looks good! question about the error handling: I noticed that a lot of the if err checks return the error directly. Do we feel that the error returned provides enough context? If not, we can consider wrapping them.

[austingebauer]

Good point @raymonstah. Added more error context and moved some context around in 3bcea36.

[vinay-gopalan]

Looks great, thanks for working through this!