[3.12] gh-66543: Fix mimetype.guess_type() (GH-117217) (GH-117256)

Fix parsing of the following corner cases:

* URLs with only a host name
* URLs containing a fragment
* URLs containing a query
* filenames with only a UNC sharepoint on Windows

(cherry picked from commit 9654daf793b534b44a831c80f43505ab9e380f1f)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
Co-authored-by: Dong-hee Na <donghee.na92@gmail.com>