Support wildcard expression to load multiple files from GCS

## Tell us about the problem you're trying to solve
We want to load files on GCS with wildcard expression, say about `gs://my-bucket/folder/data/data*.csv`, because it is quite common to use multiple files to express single data.

## Describe the solution you’d like
It seems that `URLFile` seems to accept only a single file. I am not sure the best solution. We might have to change the specification to deal with file(s).
https://github.com/airbytehq/airbyte/blob/d4267818ae0f81f584f856b6b208ee76d774e15a/airbyte-integrations/connectors/source-file/source_file/client.py#L51

## Describe the alternative you’ve considered or used
Technically, we might be able to read files one by one. But, it is very annoying.

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