Reorganize cuDF Python docs (NVIDIA#10691)

This PR is composed of two high-level changes:

* Replaces the use of ReStructuredText with [MyST Markdown](https://myst-parser.readthedocs.io/en/latest/). I used [rst2myst](https://github.com/executablebooks/rst2myst) for this and it worked pretty well. The rationale for this change is simple: we use `myst-nb` to render notebooks into documentation, and for consistency, it's nice to use `myst-parser` to parse the rest of our docs too. As a matter of opinion, I think Markdown is simpler and more familiar to most developers.

* Reorganizes the docs (see below):

Prior to this PR, the cuDF documentation was divided into 3 sections:

* A user guide
* A "Basics" section
* API reference

The distinction between the first two sections was never clear. I've gone ahead and merged those into a single section named "User Guide". This is also more consistent with Pandas.

This PR also makes a couple of other changes:

- Renamed the "Basics" page under the previous "Basics" section to "Data Types", as that reflects its contents more accurately. I also modified the content here a bit.
- Renamed the "10 minutes to CuPy and CuDF" notebook to "Interoperability between CuPy and CuDF" as that more accurately describes what that page is about.

----

Compare the TOC from this PR (below) with our [currently published docs](https://docs.rapids.ai/api/cudf/stable/).

<img width="710" alt="Screen Shot 2022-04-20 at 1 13 04 PM" src="https://user-images.githubusercontent.com/3190405/164286913-2e3bfd2a-caa7-4324-9cad-bd131058999f.png">

Authors:
  - Ashwin Srinath (https://github.com/shwina)
  - Mike McCarty (https://github.com/mmccarty)
  - GALI PREM SAGAR (https://github.com/galipremsagar)

Approvers:
  - GALI PREM SAGAR (https://github.com/galipremsagar)
  - Mike McCarty (https://github.com/mmccarty)
  - Bradley Dice (https://github.com/bdice)

URL: rapidsai/cudf#10691

docs/cudf/source/_static/params.css

@@ -50,11 +50,17 @@ table.io-supported-types-table thead{
 
 }
 
+/* Used to make special-table scrollable when it overflows */
+.special-table-wrapper {
+    width: 100%;
+    overflow: auto !important;
+}
+
 .special-table td, .special-table th {
     border: 1px solid #dee2e6;
 }
 
-/* Needed to resolve https://github.com/executablebooks/jupyter-book/issues/1611 */ 
+/* Needed to resolve https://github.com/executablebooks/jupyter-book/issues/1611 */
 .output.text_html {
     overflow: auto;
 }