Create the monolith VM no N1 type already present in all region

[christianmarangoni]

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Describe the bug

During the step of make monolith-deploy this message is present if you choose a region where n1 gce instance instance is not present

ERROR: (gcloud.compute.instances.create) Could not fetch resource:
 - Invalid value for field 'resource.machineType': 'https://compute.googleapis.com/compute/v1/projects/bank-of-anthos-xxxx/zones/europe-west8-a/machineTypes/n1-standard-1'. Machine type with name 'n1-standard-1' does not exist in zone 'europe-west8-a'."

Use `gcloud compute machine-types list --zones` to see the available machine  types.
make: *** [Makefile:61: monolith-deploy] Error 

To Reproduce

Follow the steps in the guide of migration monolith here https://cloud.google.com/migrate/containers/docs/migrating-monolith-vm-overview-setup

1. choose in the step 1 a zone like europe-west8 to export export ZONE=europe-west8-a
2. Follow the step to step 3 of the guide
3. Recive the errore during the make monolith-deploy

   
   ERROR: (gcloud.compute.instances.create) Could not fetch resource:
   - Invalid value for field 'resource.machineType': 'https://compute.googleapis.com/compute/v1/projects/bank-of-anthos-xxxx/zones/europe-west8-a/machineTypes/n1-standard-1'. Machine type with name 'n1-standard-1' does not exist in zone 'europe-west8-a'."

Use gcloud compute machine-types list --zones to see the available machine types. make: *** [Makefile:61: monolith-deploy] Error

### Logs  

ERROR: (gcloud.compute.instances.create) Could not fetch resource:

• Invalid value for field 'resource.machineType': 'https://compute.googleapis.com/compute/v1/projects/bank-of-anthos-xxxx/zones/europe-west8-a/machineTypes/n1-standard-1'. Machine type with name 'n1-standard-1' does not exist in zone 'europe-west8-a'."

Use gcloud compute machine-types list --zones to see the available machine types. make: *** [Makefile:61: monolith-deploy] Error

### Screenshots 
Not applicable 

### Environment 
region europe-west8 and other region where n1 is not present

[bourgeoisor]

That machine type is hard-coded here: https://github.com/GoogleCloudPlatform/bank-of-anthos/blob/main/src/ledgermonolith/scripts/deploy-monolith.sh#L69

I'll have to spend some time thinking how I want to approach this. In the mean time, feel free to select another region that does support that machine type.

[minherz]

@bourgeoisor do we plan to take this forward?

[bourgeoisor]

I do want to make sure this process is smooth so either I'll fix it here, or will tweak relevant tutorials to mention this requirement. Let's keep this issue open in the meantime.