[Python][Dataset] Infer the filesystem from the first path if multiple paths are passed to dataset()

[asfimport]

See conversation #6505 (comment)

Reporter: Krisztian Szucs / @kszucs

_{Note: This issue was originally created as ARROW-8400. Please see the migration documentation for further details.}

[thisisnic]

This issue hasn't had activity in a long time. If it's still being worked on, please leave a comment. Otherwise, it will be closed on 23rd June.

Labelled Status: Stale-Warning for tracking.