Fix/filter/avoid test warnings

[hugovk]

Running plain pytest warns:

======================================================== warnings summary ========================================================
Tests/test_file_tiff.py: 1 warning
Tests/test_tiff_crashes.py: 13 warnings
  /Users/hugo/github/Pillow/src/PIL/TiffImagePlugin.py:812: UserWarning: Truncated File Read
    warnings.warn(str(msg))

Tests/test_map.py::test_tobytes
  /Users/hugo/github/Pillow/src/PIL/Image.py:2916: DecompressionBombWarning: Image size (151587072 pixels) exceeds limit of 89478485 pixels, could be decompression bomb DOS attack.
    warnings.warn(

-- Docs: https://docs.pytest.org/en/stable/warnings.html

Runing pytest -Wall with all warnings enabled adds some more:

======================================================== warnings summary ========================================================
Tests/test_file_tiff.py: 2 warnings
Tests/test_tiff_crashes.py: 26 warnings
  /Users/hugo/github/Pillow/src/PIL/TiffImagePlugin.py:812: UserWarning: Truncated File Read
    warnings.warn(str(msg))

Tests/test_imagepalette.py::test_reload
  /Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/_pytest/python.py:183: ResourceWarning: unclosed file <_io.BufferedReader name='Tests/images/hopper.gif'>
    result = testfunction(**testargs)

Tests/test_map.py::test_tobytes
  /Users/hugo/github/Pillow/src/PIL/Image.py:2916: DecompressionBombWarning: Image size (151587072 pixels) exceeds limit of 89478485 pixels, could be decompression bomb DOS attack.
    warnings.warn(

-- Docs: https://docs.pytest.org/en/stable/warnings.html

[radarhere]

For the record, the crash image was removed in #5561

[hugovk]

Yep, Tests/images/crash-81154a65438ba5aaeca73fd502fa4850fbde60f8.tif shows up when running install_extra_test_images.sh, and we already ignore the other https://github.com/python-pillow/pillow-depends/tree/master/test_images files.