[3.13] gh-77894: Fix a crash when the GC breaks a loop containing a memoryview (GH-123898) (#123936)

gh-77894: Fix a crash when the GC breaks a loop containing a memoryview (GH-123898)

Now a memoryview object can only be cleared if there are no buffers
that refer it.
(cherry picked from commit a1dbf2ea69acc6ccee6292709af1dadd55c068be)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>