feat(billing): Add cli subcommand for monthly active user counts

internal/proto/controller/api/resources/billing/v1/billing.proto

@@ -11,7 +11,7 @@ option go_package = "github.com/hashicorp/boundary/sdk/pbs/controller/api/resour
 
 message ActiveUsers {
   // Output only. The number of active users between the start time and end time.
-  uint64 count = 1; // @gotags: `class:"public"`
+  uint32 count = 1; // @gotags: `class:"public"`
 
   // Output only. The start time of the active users count, inclusive.
   google.protobuf.Timestamp start_time = 2 [json_name = "start_time"]; // @gotags: class:"public"

internal/proto/controller/api/services/v1/billing_service.proto

@@ -7,7 +7,6 @@ package controller.api.services.v1;
 
 import "controller/api/resources/billing/v1/billing.proto";
 import "google/api/annotations.proto";
-import "google/protobuf/timestamp.proto";
 import "protoc-gen-openapiv2/options/annotations.proto";
 
 option go_package = "github.com/hashicorp/boundary/internal/gen/controller/api/services;services";