Update for the tinyDTLS submodule using a github source repo

Squashed commit of the following:

commit f25b8a4ab68165883a4d22032994e51cd4367ed9
Author: Martin <martinbrandthilde@gmail.com>
Date:   Thu Sep 5 23:32:44 2024 +0200

    add submodule tinydtls new version

commit 945a4e09b90a831713f948d567186f7d4382c891
Author: Martin <martinbrandthilde@gmail.com>
Date:   Thu Sep 5 23:31:41 2024 +0200

    removed submodule tinydtls old version

commit 1876aa3a1916fd447153d2cbd3ff934bf3d55cba
Author: Martin <martinbrandthilde@gmail.com>
Date:   Thu Sep 5 23:07:07 2024 +0200

    update submodule

commit 16f310c7337c20e8dee9523b57c39b8f91516317
Author: Martin <martinbrandthilde@gmail.com>
Date:   Thu Sep 5 22:54:26 2024 +0200

    fix build errors, add uint8_t for tinydtls/sha2.c

Fix #12

Cleaning up in __del__ (or any __del__, really) triggered pypy's checks
for valid C API use.

Closes: https://github.com/mclab-hbrs/DTLSSocket/issues/12

Fix compatibility with Cython 3.0

Update requirements

Pin Cython dependency to <3

DTLSSocket currently does not build with Cython 3.0.0 (released 2023-07-17).

patch to compile tinydtls on Windows (MSYS2) : autoconf is found during compilation 

- add pyproject.toml to MANIFEST.in
- bump version in setup.py

 Update to devel branch

Having those in .gitignore removes clutter at `git status`, and prevents
accidental inclusion in commits.

Since 5f32f03d, its PRNG functions are fanned out into platform specific
implementations; those are included now.