Fix storages metadata & caching

[vdusek]

In the current implementation, running the following code multiple times results in errors during the parsing of the metadata files. This PR fixes it and also adds a little polishing...

import asyncio

from crawlee.request import Request
from crawlee.storages import Dataset, KeyValueStore, RequestQueue


async def main() -> None:
    dataset = await Dataset.open(name='my-dataset-42')
    await dataset.push_data({'key2': 'value'})

    kvs = await KeyValueStore.open(name='my-kvs-01')
    await kvs.set_value('key1', 'value1')

    rq = await RequestQueue.open(name='my-rq-01')
    await rq.add_request(Request.from_url('http://example.com'))


if __name__ == '__main__':
    asyncio.run(main())

[janbuchar]

Could you add a test that runs the code in the PR description?