DOC: Add plotting examples and fix broken examples
This PR improves the `pandas.plotting._misc.py` module docs by:
1. Adding example plots where they were missing from docstrings.
2. Fixing examples that were not formatted to render with
```
.. plot::
    :context: close-figs
```
3. Simplifying the syntax of some oddly-written examples.

In some cases, I replicated the examples found in the [User Guide](https://pandas.pydata.org/pandas-docs/stable/user_guide/visualization.html#plotting-tools).