pyalp: squash all local changes since github/358-python-api into sing…

…le commit

Consolidated pybind11 bindings and removed legacy duplicate source files; added a single shared binding implementation under pyalp.
Packaging moved to top-level CMake with deterministic prebuilt discovery in setup.py and support for CMAKE_BUILD_DIR so wheels are built from the CMake artifacts (avoids needing pybind11 in isolated PEP517 build environment).
Enabled module-local pybind11 registrations by default to allow importing multiple backend extension modules into the same interpreter safely; made it configurable via CMake option for cases that need cross-module sharing.
Fixed an iterator instantiation issue in matrix_wrappers.hpp by iterating directly over M.cbegin()/M.cend().
Added an in-process smoke test test_bckds_inprocess.py to validate multiple-backend imports and object creation, and updated CI to install test wheels from TestPyPI with robust retry-and-verify logic.
Updated developer docs and CI workflows to reflect the new packaging, testing, and build flows.

Update version to 0.8.40 and enhance TestPyPI installation with retry…

… logic

Bump package version to 0.8.39 in pyproject.toml

Add in-process verification for multiple backend imports and update v…

…ersion to 0.8.38

Refactor prebuilt module discovery to use a conventional out-of-sourc…

…e build directory when none is specified, preserving CI behavior.

Enhance prebuilt module discovery and metadata handling in setup.py f…

…or improved build process

Bump package version to 0.8.35 in pyproject.toml

Bump version to 0.8.34; refactor module entry and bindings for improv…

…ed organization and clarity

Remove wait_for_testpypi_release script and simplify TestPyPI propaga…

…tion handling; bump version to 0.8.33

Merge PYPI infrastructure into 358-python-api