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ARROW-7936: [Python] Fix and exercise tests on python 3.5

- added bindings for the Codec class
- support to check compiled/available compression types
- test on ubuntu 16.04 with python 3.5.2 (needs to pin dependencies because of python typing incompatibilities)
- skip the failing Filesystem.from_uri tests on python 3.5 because pathlib.Path.resolve checks that the path exists (which is not)
- run a github actions build with python 3.5.2 test for each commit

Closes #6503 from kszucs/py35 and squashes the following commits:

a5460d225 <Krisztián Szűcs> Docstrings and tests
629e03b1e <Krisztián Szűcs> trigger ci
94af5a0e3 <Krisztián Szűcs> OrderedDict
2c8521254 <Krisztián Szűcs> fix workflow syntax
649c0b528 <Krisztián Szűcs> ARROW-7936:  Fix and exercise tests on python 3.5

Authored-by: Krisztián Szűcs <szucs.krisztian@gmail.com>
Signed-off-by: Krisztián Szűcs <szucs.krisztian@gmail.com>