AtomVM CI: Fix pico, add combined uf2 & artifacts

CI for release was using outdated/wrong way of building atomvmlib-pico.uf2/atomvmlib-pico2.uf2, fixed to the new ninja building.

Moved said building to a job before the various pico builds, with the necessary upload/download of artifacts.

Removed wrong 'mv atomvmlib.uf2' segment, file is non-existent on new ninja builds, and was a leftover/duplicated code.

Added combined uf2 artifacts using uf2tool.

Upload the artifacts, so they are available for testing.

Include combined artifact in release.

Link to CI run/artifacts: https://github.com/atomvm/AtomVM/actions/runs/18612666167

These changes are made under both the "Apache 2.0" and the "GNU Lesser General Public License 2.1 or later" license terms (dual license).

SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later

Sep 15 '25 08:09 petermm

artifacts from latest https://github.com/atomvm/AtomVM/actions/runs/18612666167

Oct 18 '25 08:10 petermm

rebased, and good to go..

doesn't do artifacts for jit/risc - believe that is better handled in subsequent PR.

Latest run artifacts: https://github.com/atomvm/AtomVM/actions/runs/20174070999?pr=1826

Dec 12 '25 18:12 petermm