implement better authorizer config and management

Currently authorizer configuration for samples/tests is managed in `internal/iam/authorizers.go`. Instead of separate authorizer factories for each resource, it would be easier for users to understand if we used one authorizer factory parameterizable by resource.

If any authorizers require such divergent configuration that a different factory is needed, we should consider addressing this upstream in the SDK itself. Key Vault dataplane client may be a case for that.

Start with internal/iam/authorizers.go and inspect how the separate authorizer factories are configured for samples and tests. Compare their resource-specific differences, including the Key Vault dataplane client case, and determine whether they can use one parameterizable factory or require an upstream SDK change. Done means the configuration is simplified without losing required divergent behavior.

Written by the indexing model from the issue text.