Mass format python with yapf

- Add `.style.yapf` with configuration to use Google style.
- Run `yapf` on all `.py` files in this repo.
- Manually fix one trailing space in a doc string.
- Run `git cl format runtime` to satisfy presubmit.

Change-Id: I7e6bd11e91f07926b9188362599af398551eed79
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/111600
Commit-Queue: Nate Bosch <nbosch@google.com>
Reviewed-by: Alexander Thomas <athom@google.com>

tools/write_revision_file.py

@@ -8,27 +8,26 @@ import os
 import sys
 import utils
 
+
 def ParseArgs(args):
-  args = args[1:]
-  parser = argparse.ArgumentParser(
-      description='A script to write the version string to a file')
+    args = args[1:]
+    parser = argparse.ArgumentParser(
+        description='A script to write the version string to a file')
 
-  parser.add_argument('--output', '-o',
-      type=str,
-      required=True,
-      help='File to write')
+    parser.add_argument(
+        '--output', '-o', type=str, required=True, help='File to write')
 
-  return parser.parse_args(args)
+    return parser.parse_args(args)
 
 
 def Main(argv):
-  args = ParseArgs(argv)
-  revision = utils.GetGitRevision()
-  if revision is not None:
-    with open(args.output, 'w') as f:
-      f.write('%s\n' % revision)
-  return 0
+    args = ParseArgs(argv)
+    revision = utils.GetGitRevision()
+    if revision is not None:
+        with open(args.output, 'w') as f:
+            f.write('%s\n' % revision)
+    return 0
 
 
 if __name__ == '__main__':
-  sys.exit(Main(sys.argv))
+    sys.exit(Main(sys.argv))