### Is there an existing issue for this?

- [X] I have searched the existing issues

### Feature description

I prefer not to use the real regions when doing tests or local stuff to make sure that if it accidentally picks up real credentials, it won't actually create or interact with resources in AWS. This used to work find in localstack - I even dug through the code to find that there is an option in the `RegionStore` to disable validation of the region string. At some point, you removed any way to disable that validation though, which means it just fails all requests using a custom region.

### 🧑‍💻 Implementation

There's already a flag that is passed to the account and region store constructors to disable validation. Seems like an environment variable or configuration flag to disable validation could be propagated.

### Anything else?

_No response_
"""
Base class and utilities for provider stores.
Stores provide storage for AWS service providers and are analogous to Moto's BackendDict.
By convention, Stores are to be defined in `models` submodule of the service
by subclassing BaseStore e.g. `localstack.services.sqs.models.SqsStore`
Also by convention, cross-region and cross-account attributes are declared in CAPITAL_CASE
    class SqsStore(BaseStore):
        queues: dict[str, SqsQueue] =  LocalAttribute(default=dict)
        DELETED: dict[str, float] = CrossRegionAttribute(default=dict)
Stores are then wrapped in AccountRegionBundle
    sqs_stores = AccountRegionBundle('sqs', SqsStore)
Access patterns are as follows
    account_id = '001122334455'
    sqs_stores[account_id]  # -> RegionBundle
    sqs_stores[account_id]['ap-south-1']  # -> SqsStore
    sqs_stores[account_id]['ap-south-1'].queues  # -> {}
There should be a single declaration of a Store for a given service. If a service
has both Community and Pro providers, it must be declared as in Community codebase.
All Pro attributes must be declared within.
While not recommended, store classes may define member helper functions and properties.
"""
import re
from collections.abc import Callable