HVT-2807 Add cluster scaling tests for Azure

[aoripov]

🛠️ Description

Add cluster scaling tests for Azure

🏗️ Acceptance tests

• Are there any feature flags that are required to use this functionality?
• Have you added an acceptance test for the functionality being added?
• Have you run the acceptance tests on this branch?

Output from acceptance testing:

$  TF_LOG_PATH=scale.out.text TF_LOG=TRACE TF_ACC=1 go test ./internal/... -parallel 20 -v -run=TestAccVaultClusterAzure -timeout 240m
testing: warning: no tests to run
PASS
ok  	github.com/hashicorp/terraform-provider-hcp/internal/clients	(cached) [no tests to run]
testing: warning: no tests to run
PASS
ok  	github.com/hashicorp/terraform-provider-hcp/internal/consul	0.436s [no tests to run]
testing: warning: no tests to run
PASS
ok  	github.com/hashicorp/terraform-provider-hcp/internal/input	0.325s [no tests to run]
=== RUN   TestAccVaultClusterAzure
=== PAUSE TestAccVaultClusterAzure
=== CONT  TestAccVaultClusterAzure
--- PASS: TestAccVaultClusterAzure (3479.18s)
PASS
ok  	github.com/hashicorp/terraform-provider-hcp/internal/provider	3479.976s
...

[bcmdarroch]

Passed locally:

--- PASS: TestAccVaultClusterAzure (4216.82s)