bump msgq: drop scons build

[mpurnell1]

Summary

• Removes SConscript(['msgq_repo/SConscript']) and the now-unused env_swaglog clone
• Replaces with env.Command() that invokes msgq's new build.py to produce libmsgq.a, libvisionipc.a, and ipc_pyx.so
• Exports msgq, visionipc, and msgq_python as File() references for downstream SConscripts

Dependencies

• Depends on Replace scons with direct clang++ build msgq#680 (msgq scons removal) being merged first
• Submodule bump to be added once that lands

Test plan

• Merge msgq PR Replace scons with direct clang++ build msgq#680
• Bump msgq submodule to new master
• Verify scons -j$(nproc) builds successfully
• Run full CI

[github-actions]

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