gh-145916: Soft-deprecate ctypes.util.find_library (GH-145919)

* Put the "Loading shared libraries" section first
  * Adjust formatting at the end of the section
* In "Finding shared libraries", add more text about what's going on
* Move the stub function doc for find_library into "Finding shared libraries"
  * Also move the sister function, find_msvcrt. That's on the chopping block,
    but not removed now.