v4.2.0

• 🌟 CPython 3.15 wheels are now built by default - without the "cpython-prerelease" enable set. It's time to build and upload these wheels to PyPI! This release includes CPython 3.15.0rc1, which is guaranteed to be ABI compatible with the final release. (#2944)
• ✨ Adds Pyodide 3.15 support with the cp315-pyodide_wasm32 build identifier, using Pyodide 315.0.0a2. These are also stable wrt. the final release. (#2958)
• 🐛 Retries a failed download six times with exponential backoff, so short network outages no longer stop a build. A 4xx response is still reported at once. (#2953)
• 🐛 Accepts default as a build-frontend value on Pyodide, and accepts pyodide-build in the top-level table and in overrides (#2951)
• 🛠 Holds pip back on GraalPy, where newer pip breaks the build (#2955)
• 🛠 Updates Pyodide to 314.0.4 (#2949, #2952)
• 🛠 Updates dependencies and container pins (#2952, #2960)
• 💼 Updates CI action pins (#2948, #2954)
• 🧪 Uses pp311 for the abi3 test, and deletes test_overridden_pip_constraint, which is not necessary since #2583 (#2956, #2957)