### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

When a scheduled rules runs, an empty event is generated and sent to targets.

### Expected Behavior

An event like this sample should be sent.
```json
{
  "version": "0",
  "id": "89d1a02d-5ec7-412e-82f5-13505f849b41",
  "detail-type": "Scheduled Event",
  "source": "aws.events",
  "account": "123456789012",
  "time": "2016-12-30T18:44:49Z",
  "region": "us-east-1",
  "resources": ["arn:aws:events:us-east-1:123456789012:rule/SampleRule"],
  "detail": {}
}
```

### How are you starting LocalStack?

With a docker-compose file

### Steps To Reproduce

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

    docker-compose up

#### Client commands (e.g., AWS SDK code snippet, or sequence of "awslocal" commands)

    awslocal events put-rule --name scheduled_rule --schedule-expression "rate(1 minutes)"
    awslocal events put-targets --rule scheduled_rule --targets "Id"="1","Arn"="arn:aws:logs:us-east-1:000000000000:log-group:/aws/events/echo"
    awslocal--endpoint-url=http://localhost:4566 logs tail "/aws/events/echo"

### Environment

```markdown
- OS: macOS Monterey
- LocalStack: 0.13.3
```


### Anything else?
I think [this](https://github.com/localstack/localstack/blob/1567f25a8f672f4dec23cb7cb1aadb5a744366f8/localstack/services/events/events_listener.py#L92) means an non-empty event is sent only when an input is `Constant (JSON text)`.
![image](https://user-images.githubusercontent.com/4127030/151643813-a4d1e113-dba3-41ad-8400-da57e4f674a1.png)

import pytest
from botocore.exceptions import ClientError
from pytest_httpserver import HTTPServer
from werkzeug import Request, Response
from localstack import config
from localstack.aws.api.lambda_ import Runtime
from localstack.constants import TEST_AWS_ACCOUNT_ID, TEST_AWS_REGION_NAME
from localstack.services.events.provider import _get_events_tmp_dir
from localstack.testing.aws.util import is_aws_cloud
from localstack.testing.pytest import markers
from localstack.utils.aws import arns, resources
from localstack.utils.files import load_file
from localstack.utils.strings import long_uid, short_uid, to_str
from localstack.utils.sync import poll_condition, retry
from localstack.utils.testutil import check_expected_lambda_log_events_length
from tests.aws.services.lambda_.test_lambda import TEST_LAMBDA_PYTHON_ECHO
THIS_FOLDER = os.path.dirname(os.path.realpath(__file__))
TEST_EVENT_BUS_NAME = "command-bus-dev"
EVENT_DETAIL = {"command": "update-account", "payload": {"acc_id": "0a787ecb-4015", "sf_id": "baz"}}
TEST_EVENT_PATTERN = {
    "source": ["core.update-account-command"],
    "detail-type": ["core.update-account-command"],
    "detail": {"command": ["update-account"]},
}
API_DESTINATION_AUTHS = [
    {
        "type": "BASIC",
        "key": "BasicAuthParameters",
        "parameters": {"Username": "user", "Password": "pass"},
    },