[Docs][Python] Add more info about the change in PyArrow C++ API

[asfimport]

We should add a not to the documentation: https://arrow.apache.org/docs/dev/python/integration/extending.html#c-api

explaining that the location of the PyArrow C++ header files and arrow_python lib has changed and that the users need to use the information from the Integration -> Extending page to get the new location.

Reporter: Alenka Frim / @AlenkaF
Assignee: Alenka Frim / @AlenkaF

PRs and other links:

• GitHub Pull Request #14333

_{Note: This issue was originally created as ARROW-17950. Please see the migration documentation for further details.}

[asfimport]

Joris Van den Bossche / @jorisvandenbossche:
Issue resolved by pull request 14333
#14333