Create a (customizable?) map of short location names for resources

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Infrastructure as Code Type? (Required)

not relevant

### Starter Module? (Required)

terraform - platform_landing_zone

### Use Case (Required)

There is a placeholder when customizing `resource_names` for short location (`{{azure_location_short}}`), but all it does is take the first three letters of the region name.

### Proposed Solution (Required)

It would be nicer to use the common map (like from the naming tool) to map the long name to the common short name, like `southcentralus` to `scus`.

### Important Factoids (Optional)

_No response_

### References (Optional)

_No response_

Start in the terraform platform_landing_zone starter module and locate the resource_names customization and the azure_location_short placeholder. Compare its current three-letter behavior with the common location map from the naming tool, including southcentralus to scus. Done means the customizable resource naming can use the common long-to-short location mapping.

Written by the indexing model from the issue text.