Selectively run e2e tests for serving, eventing (#547)

- Run only serving specific e2e tests locally
  ```
  E2E_TAGS="serving" ./test/e2e-tests-local.sh
  ```

 - Run only eventing specific e2e tests locally
  ```
  E2E_TAGS="eventing" ./test/e2e-tests-local.sh
  ```

 - Run all e2e tests locally
  ```
  ./test/e2e-tests-local.sh
  ```

test/e2e-tests-local.sh

@@ -26,4 +26,4 @@ echo "📋 Formatting"
 go fmt ${base}/test/e2e/...
 
 echo "🧪  Testing"
-go test ${base}/test/e2e/ -test.v --tags 'e2e' "$@"
+go test ${base}/test/e2e/ -test.v -tags "e2e ${E2E_TAGS}" "$@"

test/e2e/basic_workflow_test.go

@@ -13,6 +13,7 @@
 // limitations under the License.
 
 // +build e2e
+// +build !eventing
 
 package e2e
 

test/e2e/revision_test.go

@@ -13,6 +13,7 @@
 // limitations under the License.
 
 // +build e2e
+// +build !eventing
 
 package e2e
 

test/e2e/route_test.go

@@ -13,6 +13,7 @@
 // limitations under the License.
 
 // +build e2e
+// +build !eventing
 
 package e2e
 

test/e2e/service_options_test.go

@@ -13,6 +13,7 @@
 // limitations under the License.
 
 // +build e2e
+// +build !eventing
 
 package e2e
 

test/e2e/service_test.go

@@ -13,6 +13,7 @@
 // limitations under the License.
 
 // +build e2e
+// +build !eventing
 
 package e2e
 

test/e2e/source_list_types_test.go

@@ -13,6 +13,7 @@
 // limitations under the License.
 
 // +build e2e
+// +build !serving
 
 package e2e
 

test/e2e/traffic_split_test.go

@@ -13,6 +13,7 @@
 // limitations under the License.
 
 // +build e2e
+// +build !eventing
 
 package e2e