fix: Include nested packages in generated setup.py (closes #575)

[tedo-benchling]

When openapi-python-client is used to with the
--meta=setup option the generated setup.py needs to
use setuptools.find_packages() to find the top-level
and all of the nested pacakges in the directory
so that distributions include them

[codecov]

Codecov Report

Merging #576 (26f7aca) into main (65cf25b) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##              main      #576   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           49        49           
  Lines         1713      1713           
=========================================
  Hits          1713      1713           

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[tedo-benchling]

Before:

Archive:  dist/foo_api_client-1.0.0.dev0-py3-none-any.whl
  Length      Date    Time    Name
---------  ---------- -----   ----
      121  01-08-2022 00:43   foo_api_client/__init__.py
     1660  01-08-2022 00:43   foo_api_client/client.py
       25  01-08-2022 00:43   foo_api_client/py.typed
      984  01-08-2022 00:43   foo_api_client/types.py
     4296  01-25-2022 18:57   foo_api_client-1.0.0.dev0.dist-info/METADATA
       92  01-25-2022 18:57   foo_api_client-1.0.0.dev0.dist-info/WHEEL
       41  01-25-2022 18:57   foo_api_client-1.0.0.dev0.dist-info/top_level.txt
      874  01-25-2022 18:57   foo_api_client-1.0.0.dev0.dist-info/RECORD
---------                     -------
     8093                     8 files

After

Archive:  dist/foo_api_client-1.0.0.dev0-py3-none-any.whl
  Length      Date    Time    Name
---------  ---------- -----   ----
      121  01-08-2022 00:43   foo_api_client/__init__.py
     1660  01-08-2022 00:43   foo_api_client/client.py
       25  01-08-2022 00:43   foo_api_client/py.typed
      984  01-08-2022 00:43   foo_api_client/types.py
       47  01-08-2022 00:43   foo_api_client/api/__init__.py
        0  01-08-2022 00:43   foo_api_client/api/admin/__init__.py
     1237  01-08-2022 00:43   foo_api_client/api/admin/healthz.py
        0  01-08-2022 00:43   foo_api_client/api/myapi/__init__.py
     1555  01-08-2022 00:43   foo_api_client/api/myapi/api_v1.py
     1535  01-08-2022 00:43   foo_api_client/api/myapi/api_v2.py
      469  01-08-2022 00:43   foo_api_client/models/__init__.py
     2605  01-08-2022 00:43   foo_api_client/models/parameters.py
      176  01-08-2022 00:43   foo_api_client/models/parameters_convert_to.py
     1306  01-08-2022 00:43   foo_api_client/models/parameters_target_s3_data.py
     2505  01-08-2022 00:43   foo_api_client/models/params.py
     1286  01-08-2022 00:43   foo_api_client/models/params_target_s3_data.py
      156  01-08-2022 00:43   foo_api_client/models/output_format.py
     4296  01-25-2022 19:20   foo_api_client-1.0.0.dev0.dist-info/METADATA
       92  01-25-2022 19:20   foo_api_client-1.0.0.dev0.dist-info/WHEEL
       41  01-25-2022 19:20   foo_api_client-1.0.0.dev0.dist-info/top_level.txt
     2559  01-25-2022 19:20   foo_api_client-1.0.0.dev0.dist-info/RECORD
---------                     -------
    22655                     21 files

[dbanty]

LGTM, though I'm mostly leaning on your experience since I don't use setup.py 😁