replace deprecated/removed distutils copy_tree with shutil copytree

[jordivandooren]

Resolves #

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Problem

The deprecated (and in Python 3.12, removed) distutils is still referred to in happy_path_fixture.py. This could lead to problems in integration test runs.

Solution

Replace distutils.dir_util.copy_tree with shutil.copytree, which has very similar behavior.

For reference, see distutils docs:

Copy an entire directory tree src to a new location dst. Both src and dst must be directory names. If src is not a directory, raise DistutilsFileError. If dst does not exist, it is created with mkpath().

and shutil docs:

Recursively copy an entire directory tree rooted at src to a directory named dst and return the destination directory. All intermediate directories needed to contain dst will also be created by default.

Checklist

• I have read the contributing guide and understand what's expected of me.
• I have run this code in development, and it appears to resolve the stated issue.
• This PR includes tests, or tests are not required or relevant for this PR.
• This PR has no interface changes (e.g., macros, CLI, logs, JSON artifacts, config files, adapter interface, etc.) or this PR has already received feedback and approval from Product or DX.
• This PR includes type annotations for new and modified functions.