Add support for Prometheus metrics integrations

[weistrand]

CloudAMQP instances supports Prometheus metrics thus new metrics integrations has been added exporting Prometheus metrics instead of metrics coming from the RabbitMQ/LavinMQ API.

The new integrations are:

• AzureMonitor
• CloudWatch V3
• Datadog V3
• Dynatrace
• NewRelic V3
• Stackdriver V2
• Splunk V2

[tbroden84]

Example of new design for integrations worth investigating. Check if it will be easier to validate each integration type and move away from a long list of arguments. (Note: from non-prometheus integrations)

		Schema: map[string]*schema.Schema{
			"instance_id": {
				Type:        schema.TypeInt,
				Required:    true,
				ForceNew:    true,
				Description: "Instance identifier used to make proxy calls.",
			},
			"azure_monitor": {
				Type:     schema.TypeSet,
				Optional: true,
				Elem: &schema.Resource{
					Schema: map[string]*schema.Schema{
						"tenant_id": {
							Type:     schema.TypeString,
							Required: true,
						},
						"application_id": {
							Type:     schema.TypeString,
							Required: true,
						},
						"application_secret": {
							Type:      schema.TypeString,
							Required:  true,
							Sensitive: true,
						},
						"dce_uri": {
							Type:     schema.TypeString,
							Required: true,
						},
						"table": {
							Type:     schema.TypeString,
							Required: true,
						},
						"dcr_id": {
							Type:     schema.TypeString,
							Required: true,
						},
					},
				},
			},
			"cloudwatch": {
				Type:     schema.TypeSet,
				Optional: true,
				Elem: &schema.Resource{
					Schema: map[string]*schema.Schema{
						"region": {
							Type:        schema.TypeString,
							Required:    true,
							Description: "The region hosting integration service.",
						},
						"access_key_id": {
							Type:        schema.TypeString,
							Required:    true,
							Sensitive:   true,
							Description: "AWS access key identifier.",
						},
						"secret_access_key": {
							Type:        schema.TypeString,
							Required:    true,
							Sensitive:   true,
							Description: "AWS secret access key.",
						},
					},
				},
			},