Bump provider to v8

[Shr3ps]

Remove data resources signalfx_aws_services, signalfx_azure_services, signalfx_gcp_services as they were based on a no longer maintained lists in the signalfx-go library. Users may use empty list to specify "all services" instead or use strings to specify selected services.

[pdecat]

Mind to do the same for other cloud integrations?

[Shr3ps]

Buggy

splunk-terraform/terraform-provider-signalfx#456

splunk-terraform/terraform-provider-signalfx#457

[Poil]

Perhaps we can put default value for services

	services = [
		"microsoft.analysisservices/servers",
		"microsoft.apimanagement/service",
		"microsoft.automation/automationaccounts",
		"microsoft.batch/batchaccounts",
		"microsoft.cache/redis",
		"microsoft.cdn/cdnwebapplicationfirewallpolicies",
		"microsoft.cdn/profiles",
		"microsoft.classiccompute/virtualmachines",
		"microsoft.cognitiveservices/accounts",
		"microsoft.compute/virtualmachines",
		"microsoft.compute/virtualmachinescalesets",
		"microsoft.compute/virtualmachinescalesets/virtualmachines",
		"microsoft.containerinstance/containergroups",
		"microsoft.containerregistry/registries",
		"microsoft.containerservice/managedclusters",
		"microsoft.customerinsights/hubs",
		"microsoft.datafactory",
		"microsoft.datafactory/datafactories",
		"microsoft.datafactory/factories",
		"microsoft.datalakeanalytics/accounts",
		"microsoft.datalakestore/accounts",
		"microsoft.dataprotection/backupvaults",
		"microsoft.dbformariadb/servers",
		"microsoft.dbformysql/flexibleservers",
		"microsoft.dbformysql/servers",
		"microsoft.dbforpostgresql/flexibleservers",
		"microsoft.dbforpostgresql/servers",
		"microsoft.devices",
		"microsoft.devices/elasticpools",
		"microsoft.devices/elasticpools/iothubtenants",
		"microsoft.devices/iothubs",
		"microsoft.devices/provisioningservices",
		"microsoft.documentdb/databaseaccounts",
		"microsoft.eventgrid/domains",
		"microsoft.eventgrid/eventsubscriptions",
		"microsoft.eventgrid/extensiontopics",
		"microsoft.eventgrid/systemtopics",
		"microsoft.eventgrid/topics",
		"microsoft.eventhub/namespaces",
		"microsoft.hdinsight/clusters",
		"microsoft.insights/autoscalesettings",
		"microsoft.keyvault/vaults",
		"microsoft.kusto/clusters",
		"microsoft.locationbasedservices/accounts",
		"microsoft.logic/workflows",
		"microsoft.machinelearningservices/workspaces",
		"microsoft.maps/accounts",
		"microsoft.network/applicationgateways",
		"microsoft.network/azurefirewalls",
		"microsoft.network/dnszones",
		"microsoft.network/expressroutecircuits",
		"microsoft.network/frontdoors",
		"microsoft.network/loadbalancers",
		"microsoft.network/networkinterfaces",
		"microsoft.network/publicipaddresses",
		"microsoft.network/trafficmanagerprofiles",
		"microsoft.network/virtualnetworkgateways",
		"microsoft.notificationhubs/namespaces/notificationhubs",
		"microsoft.powerbidedicated/capacities",
		"microsoft.recoveryservices/vaults",
		"microsoft.relay/namespaces",
		"microsoft.search/searchservices",
		"microsoft.servicebus/namespaces",
		"microsoft.signalrservice/signalr",
		"microsoft.signalrservice/webpubsub",
		"microsoft.sql/managedinstances",
		"microsoft.sql/servers",
		"microsoft.sql/servers/databases",
		"microsoft.sql/servers/elasticpools",
		"microsoft.storage/storageaccounts",
		"microsoft.storage/storageaccounts/blobservices",
		"microsoft.storage/storageaccounts/fileservices",
		"microsoft.storage/storageaccounts/queueservices",
		"microsoft.storage/storageaccounts/tableservices",
		"microsoft.streamanalytics/streamingjobs",
		"microsoft.web",
		"microsoft.web/hostingenvironments/multirolepools",
		"microsoft.web/hostingenvironments/workerpools",
		"microsoft.web/serverfarms",
		"microsoft.web/sites",
		"microsoft.web/sites/slots"
	]