STYLE: #22885, Moved all setup imports to bottom of benchmark files and added noqa: F401 to each
- [x] closes #22885 
- [ ] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

#22885 

Following the suggestions of @datapythonista, I moved all the `setup` imports for the benchmark files to the end of each file and added a `# noqa: F401` like so:

`from .pandas_vb_common import setup  # noqa: F401`

Now, `flake8` only returns the following two errors in `asv_bench`:

```
./benchmarks/strings.py:95:9: E731 do not assign a lambda expression, use a def
./benchmarks/io/excel.py:6:1: F401 '..pandas_vb_common.BaseIO' imported but unused
```

These may be expected, but I wanted to mention them here just in case they need addressing.

Also, running `pytest`, I got this error:

```
usage: pytest [options] [file_or_dir] [file_or_dir] [...]
pytest: error: unrecognized arguments: --strict-data-files
  inifile: /pandas/setup.cfg
  rootdir: /pandas
```

I found a discussion on it at #22700, but there didn't seem to be a definitive solution. Open to guidance on this.

Please let me know if any corrections are needed. Thanks!