[Python][Docs] Update/rearrange Data Types section and add FixedShapeTensorType

### Describe the enhancement requested

The [Data Types and In-Memory Data Model](https://arrow.apache.org/docs/dev/python/data.html) section in our documentation is already quite long and includes a lot of things. With the fixed shape tensor canonical extension type (and RunEndEncodedType) added to pyarrow, this section could be rearranged and should include newly added Data Types also.

### Component(s)

Documentation

Start with the Data Types and In-Memory Data Model section in the linked pyarrow documentation and review how its existing topics are organized. Rearrange the section and add the fixed shape tensor canonical extension type (FixedShapeTensorType) and RunEndEncodedType so the newly added data types are covered.

Written by the indexing model from the issue text.