### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

The documentation states that when setting DYNAMODB_SHARE_DB=1 DynamodDB will use a single database for each credential and region. This doesn't work when LocalStack is started from CLI. For example:

`DYNAMODB_SHARE_DB=1 localstack start -d`

In Docker logs you can find:
INFO:localstack.services.dynamodb.server: SharedDb:     false

At least it seems that the environment variable is missing from CONFIG_ENV_VARS which is used for passing the environment variables to container.

Tried the following fix and at least after brief testing it solves the issue:
https://github.com/jvuori/localstack/commit/6bb4a3c68c8675b9548e0f5eb8028397d9ee5a47
Feel free to pull if the fix is appropriate. (Sorry, no unit test...)

### Expected Behavior

`DYNAMODB_SHARE_DB=1 localstack start -d`
should start DynamoDB with:

INFO:localstack.services.dynamodb.server: SharedDb:     true

### How are you starting LocalStack?

With the `localstack` script

### Steps To Reproduce

#### How are you starting localstack (e.g., `bin/localstack` command, arguments, or `docker-compose.yml`)

DYNAMODB_SHARE_DB=1 localstack start -d


### Environment

```markdown
- OS: Windows + WSL2 + Docker CE running inside WSL2
- LocalStack: 0.14.1
```


### Anything else?

_No response_
if service not in self._provider_config:
            self._provider_config[service] = provider
    def set_provider(self, service: str, provider: str):
        self._provider_config[service] = provider
    def bulk_set_provider_if_not_exists(self, services: List[str], provider: str):
        for service in services:
            self.set_provider_if_not_exists(service, provider)
    def __getitem__(self, item):
        return self.get_provider(item)
    def __setitem__(self, key, value):
        self.set_provider(key, value)
    def __len__(self):
        return len(self._provider_config)
    def __iter__(self):
        return self._provider_config.__iter__()
SERVICE_PROVIDER_CONFIG = ServiceProviderConfig("default")
SERVICE_PROVIDER_CONFIG.load_from_environment()
if is_in_docker:
    dirs = Directories.for_container()
else:
    dirs = Directories.from_config()
dirs.mkdirs()
for path in [dirs.config, os.path.join(dirs.tmp, ".localstack")]:
    if path and os.path.isfile(path):
        print(
            f"warning: the config file .localstack is deprecated and no longer used, "
            f"please remove it by running rm {path}"
        )