[3.14] gh-143672: Add more tests for struct.pack_into() (GH-143901) (GH-143902)

Add tests for negative offset, out of bound offset, invalid type of offset,
non-writeable buffer, non-continuous buffer, invalid type of buffer.

Repeat all tests for struct.Struct.pack_into().
(cherry picked from commit 66680f1230e51b8274279964f8d2278d12285eb3)

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