Support for custom resource build suffix

#### Description

Add an optional parameter `custom_resource_build_suffix`, that is similar to `custom_resource_build_prefix`. If this parameter is set the temporary resources will be named accordingly. E.g. Azure KeyVault resource will be named `custom_resource_build_prefix`resourcetype`custom_resource_build_suffix`
If `custom_resource_build_suffix` is not set the name will be `custom_resource_build_prefix` + resourcetype + 5 character random alphanumeric string

#### Use Case(s)

In case of using Azure Policy that enforces special naming convention packer script will fail.

Start by locating the existing handling for custom_resource_build_prefix in the Azure resource naming code and its tests. Add coverage for a configured suffix and for the existing five-character random fallback; done means temporary resources follow the requested naming convention without changing the default behavior.

Written by the indexing model from the issue text.