feat(api): add prometheus metric coderd_workspace_builds_total (#6314)

This PR adds the prometheus metric coderd_workspace_builds_total.
It measures the total number of workspace builds, along with a number of labels intended to be useful for an operator debugging a failed workspace build trying to discover the scope of the issue.

coderd/provisionerdserver/provisionerdserver.go

@@ -210,6 +210,8 @@ func (server *Server) AcquireJob(ctx context.Context, _ *proto.Empty) (*proto.Ac
 					WorkspaceOwnerEmail: owner.Email,
 					WorkspaceId:         workspace.ID.String(),
 					WorkspaceOwnerId:    owner.ID.String(),
+					TemplateName:        template.Name,
+					TemplateVersion:     templateVersion.Name,
 				},
 			},
 		}

coderd/provisionerdserver/provisionerdserver_test.go

@@ -206,6 +206,8 @@ func TestAcquireJob(t *testing.T) {
 					WorkspaceOwnerEmail: user.Email,
 					WorkspaceId:         workspace.ID.String(),
 					WorkspaceOwnerId:    user.ID.String(),
+					TemplateName:        template.Name,
+					TemplateVersion:     version.Name,
 				},
 			},
 		})