CodeHealth: Migrate PRESUBMITs from Python 2 to Python 3

This CL includes:
* set Pylint version to 2.7
* pass skip_shebang_check=True to RunUnitTestsInDirectory

And fixes some Pylint warnings:
* W0406: fix import-self
* E1101: Set name and aliases as an abstract property in
  encode_pdf_filter.py since name and aliases are introduced in
  subclasses.
* E0012: Remove Py2 hint of # pylint: disable=relative-import
* R0205: Replace all "class ClassName(objects)" with "class ClassName"
* E1120: Ignore this error. see
  https://github.com/PyCQA/pylint/issues/3563
* W0707: explicitly re-raising using the 'from' keyword

Bug: pdfium:1674, chromium:1262354, chromium:1262297
Change-Id: I205d254514f1ae667af818c789b5e6d89a061c68
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/87270
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index 55d417c..fa7241f 100644
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -496,6 +496,9 @@
                 input_api,
                 output_api,
                 full_path,
-                files_to_check=[r'^PRESUBMIT_test\.py$']))
+                files_to_check=[r'^PRESUBMIT_test\.py$'],
+                run_on_python2=not USE_PYTHON3,
+                run_on_python3=USE_PYTHON3,
+                skip_shebang_check=True))
 
   return results