Extend support for tag bindings to more modules (#2307)

* fix kms tag bindings

* bigquery dataset

* fix bigquery

* cloud run

* normalize variable type

* rename gcs heading

* kms example test

* fix bigquery

* fix cloud run

* cloud run v2

modules/kms/variables.tf

@@ -119,6 +119,6 @@ variable "project_id" {
 variable "tag_bindings" {
   description = "Tag bindings for this keyring, in key => tag value id format."
   type        = map(string)
-  default     = {}
   nullable    = false
+  default     = {}
 }