docs(eventarc): update ReadMes (GoogleCloudPlatform#5348)

## Description

Fixes GoogleCloudPlatform#5057

Note: It's a good idea to open an issue first for discussion.

## Checklist
- [ ] I have followed [Sample Guidelines from AUTHORING_GUIDE.MD](https://github.com/GoogleCloudPlatform/python-docs-samples/blob/master/AUTHORING_GUIDE.md)
- [ ] README is updated to include [all relevant information](https://github.com/GoogleCloudPlatform/python-docs-samples/blob/master/AUTHORING_GUIDE.md#readme-file)
- [ ] **Tests** pass:   `nox -s py-3.6` (see [Test Environment Setup](https://github.com/GoogleCloudPlatform/python-docs-samples/blob/master/AUTHORING_GUIDE.md#test-environment-setup))
- [ ] **Lint** pass:   `nox -s lint` (see [Test Environment Setup](https://github.com/GoogleCloudPlatform/python-docs-samples/blob/master/AUTHORING_GUIDE.md#test-environment-setup))
- [ ] These samples need a new **API enabled** in testing projects to pass (let us know which ones)
- [ ] These samples need a new/updated **env vars** in testing projects set to pass (let us know which ones)
- [ ] Please **merge** this PR for me once it is approved.
- [ ] This sample adds a new sample directory, and I updated the [CODEOWNERS file](https://github.com/GoogleCloudPlatform/python-docs-samples/blob/master/.github/CODEOWNERS) with the codeowners for this sample

Author: averikitsch

eventarc/audit-storage/README.md

@@ -1,68 +1,7 @@
 # Cloud Eventarc - Cloud Storage via Audit Logs tutorial
 
-This sample shows how to create a service that processes GCS using [the CloudEvents SDK](https://github.com/cloudevents/sdk-python).
+This sample shows how to create a service that processes GCS using 
+[the CloudEvents SDK](https://github.com/cloudevents/sdk-python).
 
-## Setup
-
-Configure environment variables:
-
-```sh
-MY_RUN_SERVICE=gcs-service
-MY_RUN_CONTAINER=gcs-container
-MY_GCS_BUCKET=gcs-bucket # Must be globally unique.
-```
-
-## Quickstart
-
-Deploy your Cloud Run service:
-
-```sh
-gcloud builds submit \
-  --tag gcr.io/$(gcloud config get-value project)/$MY_RUN_CONTAINER
-gcloud run deploy $MY_RUN_SERVICE \
-  --image gcr.io/$(gcloud config get-value project)/$MY_RUN_CONTAINER \
-  --platform managed
-```
-
-Create a _single region_ Cloud Storage bucket:
-
-```sh
-gsutil mb -p $(gcloud config get-value project) \
-  -l us-central1 \
-  gs://"$MY_GCS_BUCKET"
-```
-
-Create Cloud Storage trigger:
-
-```sh
-gcloud beta eventarc triggers create my-gcs-trigger \
-  --destination-run-service $MY_RUN_SERVICE  \
-  --matching-criteria type=google.cloud.audit.log.v1.written \
-  --matching-criteria methodName=storage.buckets.update \
-  --matching-criteria serviceName=storage.googleapis.com \
-  --matching-criteria resourceName=projects/_/buckets/"$MY_GCS_BUCKET"
-```
-
-## Test
-
-Test your Cloud Run service by creating a GCS event:
-
-```sh
-gsutil defstorageclass set STANDARD gs://$MY_GCS_BUCKET
-```
-
-Observe the Cloud Run service printing upon receiving an event in Cloud Logging:
-
-```sh
-gcloud logging read "resource.type=cloud_run_revision AND \
-  resource.labels.service_name=$MY_RUN_SERVICE" \
-  --project $(gcloud config get-value project) \
-  --limit 30 \
-  --format 'value(textPayload)'
-```
-
-One of the logs you'll see shows the Run service confirming the event was received:
-
-```
-GCS CloudEvent type: storage.googleapis.com/projects/_/buckets/gcs-bucket
-```
+See tutorial, [Quickstart: Receiving Cloud Storage events](https://cloud.google.com/eventarc/docs/run/quickstart?hl=en#python), 
+tutorial for instructions for setting up and deploying this sample application.

eventarc/pubsub/README.md

@@ -3,24 +3,38 @@
 This sample shows how to create a service that processes Pub/Sub events using 
 [the CloudEvents SDK](https://github.com/cloudevents/sdk-python).
 
+## Setup
+
+Set the `gcloud` configuration variables:
+
+```sh
+gcloud config set project <PROJECT_ID>
+gcloud config set run/region us-central1
+gcloud config set run/platform managed
+gcloud config set eventarc/location us-central1
+```
+
 ## Quickstart
 
 Deploy your Cloud Run service:
 
 ```sh
 gcloud builds submit \
   --tag gcr.io/$(gcloud config get-value project)/eventarc-pubsub
+
 gcloud run deploy eventarc-pubsub \
   --image gcr.io/$(gcloud config get-value project)/eventarc-pubsub \
-  --platform managed
+  --platform managed \
+  --allow-unauthenticated
 ```
 
 Create a Cloud Eventarc trigger, which will also create a Pub/Sub topic:
 
 ```sh
-gcloud beta eventarc triggers create pubsub-trigger \
-  --destination-run-service eventarc-pubsub \
-  --matching-criteria "type=google.cloud.pubsub.topic.v1.messagePublished"
+gcloud eventarc triggers create pubsub-trigger \
+  --destination-run-service=events-pubsub \
+  --destination-run-region=us-central1 \
+  --event-filters="type=google.cloud.pubsub.topic.v1.messagePublished"
 ```
 
 ## Test