backend/azurerm: exclusively using Microsoft Graph/MSAL and removing Azure Active Directory Graph/ADAL

[tombuildsstuff]

This PR finishes the migration from ADAL to MSAL for the AzureRM Backend - meaning that Microsoft Graph (and MSAL) are now used by default and Azure Active Directory Graph (and ADAL) are no longer available.

Whilst this is technically a breaking change to the config, this has been called out in the v1.1 and v1.2 releases (and is marked as deprecated in v1.2) - we believe that this shouldn't be impactful to users - and ADAL is scheduled for removal in the near future: https://docs.microsoft.com/graph/migrate-azure-ad-graph-faq

$ TF_ACC=1 go test -v ./internal/backend/remote-state/azure/ -timeout=60m
=== RUN   TestBackend_impl
--- PASS: TestBackend_impl (0.00s)
=== RUN   TestBackendConfig
--- PASS: TestBackendConfig (0.00s)
=== RUN   TestAccBackendAccessKeyBasic
--- PASS: TestAccBackendAccessKeyBasic (103.50s)
=== RUN   TestAccBackendSASTokenBasic
--- PASS: TestAccBackendSASTokenBasic (102.84s)
=== RUN   TestAccBackendOIDCBasic
--- PASS: TestAccBackendOIDCBasic (110.92s)
=== RUN   TestAccBackendMSALAzureADAuthBasic
--- PASS: TestAccBackendMSALAzureADAuthBasic (105.68s)
=== RUN   TestAccBackendMSALManagedServiceIdentityBasic
   helpers_test.go:38: Skipping test since not running in Azure
--- SKIP: TestAccBackendMSALManagedServiceIdentityBasic (0.00s)
=== RUN   TestAccBackendMSALServicePrincipalClientCertificateBasic
   backend_test.go:188: Skipping since `ARM_CLIENT_CERTIFICATE_PATH` is not specified!
--- SKIP: TestAccBackendMSALServicePrincipalClientCertificateBasic (0.00s)
=== RUN   TestAccBackendMSALServicePrincipalClientSecretBasic
--- PASS: TestAccBackendMSALServicePrincipalClientSecretBasic (111.77s)
=== RUN   TestAccBackendMSALServicePrincipalClientSecretCustomEndpoint
   backend_test.go:254: Skipping as ARM_ENDPOINT isn't configured
--- SKIP: TestAccBackendMSALServicePrincipalClientSecretCustomEndpoint (0.00s)
=== RUN   TestAccBackendAccessKeyLocked
--- PASS: TestAccBackendAccessKeyLocked (104.27s)
=== RUN   TestAccBackendServicePrincipalLocked
--- PASS: TestAccBackendServicePrincipalLocked (104.48s)
=== RUN   TestRemoteClient_impl
--- PASS: TestRemoteClient_impl (0.00s)
=== RUN   TestRemoteClientAccessKeyBasic
--- PASS: TestRemoteClientAccessKeyBasic (97.54s)
=== RUN   TestRemoteClientManagedServiceIdentityBasic
   helpers_test.go:38: Skipping test since not running in Azure
--- SKIP: TestRemoteClientManagedServiceIdentityBasic (0.00s)
=== RUN   TestRemoteClientSasTokenBasic
--- PASS: TestRemoteClientSasTokenBasic (112.18s)
=== RUN   TestRemoteClientServicePrincipalBasic
--- PASS: TestRemoteClientServicePrincipalBasic (102.07s)
=== RUN   TestRemoteClientAccessKeyLocks
--- PASS: TestRemoteClientAccessKeyLocks (100.13s)
=== RUN   TestRemoteClientServicePrincipalLocks
--- PASS: TestRemoteClientServicePrincipalLocks (103.39s)
=== RUN   TestPutMaintainsMetaData
--- PASS: TestPutMaintainsMetaData (100.11s)
PASS
ok  	github.com/hashicorp/terraform/internal/backend/remote-state/azure	1359.403s

[jackofallops]

LGTM 👍

[manicminer]

LGTM 🚀

[apparentlymart]

I don't have sufficient context to comment on the code changes here but just wanted to be explicit that you can merge this when ready since the main branch is already tracking what will become Terraform v1.3, and so we'll only be cutting v1.3 prereleases from this branch until we reach v1.3.0 final. (1.2 releases come from the v1.2 branch.)

[manicminer]

Thanks @apparentlymart, this is ready to go so merging now.

[github-actions]

Reminder for the merging maintainer: if this is a user-visible change, please update the changelog on the appropriate release branch.

[github-actions]

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