[FEA] Move pandas-related notes from Notes to pandas-compat

[vyasr]

Is your feature request related to a problem? Please describe. #8643 introduced a new rST directive pandas-compat to our documentation that allows us to collect all documentation relating to differences between cuDF methods and pandas methods. That directive enables us to much more effectively indicate to users when our behavior differs from pandas. However, we have not since made much use of this directive. Many docstrings still contain Notes sections that are essentially just descriptions of how a class/function/method differs from pandas.

Describe the solution you'd like We should convert all pandas-related Notes sections of docstrings into pandas-compat sections. Doing so should be quite straightforward by simply searching for the header Notes in all files containing public APIs. For examples on how to use the pandas-compat directive, see #8643.

Describe alternatives you've considered None

Additional context There are likely many other places where we differ from pandas that are either 1) undocumented or 2) documented in different ways. We should also aim to improve that documentation. However, that is a nebulous target since it's not immediately clear where all those places are, so this issue is just focusing on the more specific goal of replacing Notes sections, which can be easily searched for and replaced as needed.