PY-17023 Suggest different section titles for Google and Numpy docstrings

Also I removed "Params" title, since Napoleon doesn't support it and
can't render such sections.
Titles that contain multiple words are capitalized on ever word.
Actual set of headers is based on the following user suggestion:
https://youtrack.jetbrains.com/issue/PY-9795#comment=27-1122111.

python/testData/completion/sectionNamesInNumpyDocstrings.py

@@ -0,0 +1,4 @@
+def f():
+    """
+    <caret>
+    """