Connector data source versions should always be string values, however
we were using the integer checksum value for the version for fsspec
connectors. This casts that value to a string.
## Changes
* Cast the checksum value to a string when assigning the version value
for fsspec connectors.
* Adds test to validate that these connectors will assign a string value
when an integer checksum is fetched.
## Testing
Unit test added.
