Add support for custom region names in resource names

### Design

- Add a regionNameMap.sample.json file.
File structure (with sample data):
```json
{
"eastus": "eu1",
"westus:" "we1"
}
```
- Load the file contents into a `regionNameMap` variable.
- Create a `locationName` variable as follows:
```bicep
var locationName = contains(regionNameMap, location) ? regionNameMap[location] : location
```
This ensures that an overridden location name will be used, but if the location name isn't overridden, the default (Azure common region name) will be used.
- When the naming convention is turned into a naming structure, replace the `{loc}` placeholder with the `locationName` variable instead of the `location` parameter.
- When the location is sent to the valid resource name module, set an override `shortRegionName` parameter.
- Add exception for regionNameMap.json file in .gitignore.