### 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_
TRACE_LOG_LEVELS,
    TRUE_STRINGS,
)
T = TypeVar("T", str, int)
load_start_time = time.time()
class Directories:
    """
    Holds the different directories available to localstack. Some directories are shared between the host and the
    localstack container, some live only on the host and some only in the container.
    Attributes:
        static_libs: container only; binaries and libraries statically packaged with the image
        var_libs:    shared; binaries and libraries+data computed at runtime: lazy-loaded binaries, ssl cert, ...
        cache:       shared; ephemeral data that has to persist across localstack runs and reboots
        tmp:         shared; ephemeral data that has to persist across localstack runs but not reboots
        functions:   shared; volume to communicate between host<->lambda containers
        data:        shared; holds localstack state, pods, ...
        config:      host only; pre-defined configuration values, cached credentials, machine id, ...
        init:        shared; user-defined provisioning scripts executed in the container when it starts
        logs:        shared; log files produced by localstack
    """
    static_libs: str
    var_libs: str
    cache: str
    tmp: str
    functions: str
    data: str
    config: str
    init: str
    logs: str
    def __init__(