Partial pathlib port

[fsimonis]

Main changes of this PR

This PR ports ASTE python script to using pathlib.Path.

The creative coding styles of precice-aste-partition and precice-aste-evaluate make them a challenge to port.

Author's checklist

• I used the pre-commit hook and used pre-commit run --all to apply all available hooks.
• I added a test to cover the proposed changes in our test suite.
• I updated the documentation in docs/README.md.
• I added a changelog entry in ./changelog-entries/ (create if necessary).
• I updated potential breaking changes in the tutorial precice/tutorials/aste-turbine.

[davidscn]

Could you say something about the motivation to use pathlib over os.path?

[fsimonis]

Could you say something about the motivation to use pathlib over os.path?

Best to take a look at PEP 428. In general:

• Object-oriented interface instead of relying on str
• Support for chaining and easier queries
• Doesn't mix with buildins by default. Which can easily result in bugs when using str