fix: support multiple user managed identities

[fabiomatavelli]

Hey guys,

This PR solves the issue of login to Azure when running on a VM with multiple User Assigned MSI IDs.
I've upgraded the tokenprovider_msi.go to use the most recent Azure Active Directory Login NewServicePrincipalTokenFromManagedIdentity method instead of the deprecated NewServicePrincipalTokenFromMSI.

Now, when this case happens, the user needs to specify the client_id parameter.

Co-authored-by: @eduardolmedeiros
Closes #64 #144

[jasonwbarnett]

I'd love if this was merged so I can just rebase #143 over this PR

[nywilken]

@fabiomatavelli apologies for the delayed review here. The changes look great. I rebased your branch onto the latest master and added a few small changes to before merging. Once all goes green I will merge in the changes.

Thanks for the contribution.

[nywilken]

The rebased triggered the linter to check all of the files modified (even those not in the PR). Those lint errors existed already and will be handled separately.

[nywilken]

I'd love if this was merged so I can just rebase #143 over this PR

Hi @jasonwbarnett thanks for tracking this change and apologies for the delay. Please let me know if you need help with getting your changes working after the rebase. Quickly looking at the PR it looks like you might've figured out the answer to some of your questions so I will check back once rebased to see how I can help push things forward on your end. Cheers!