Install the binaries to a prefix instead of running from the build tree

[mikelangmayr]

• Add install() rules so make install copies build outputs under ${CMAKE_INSTALL_PREFIX} (defaults to /usr/local) instead of running them from bin/ in the source tree
• Include GNUInstallDirs at the top level for CMAKE_INSTALL_BINDIR and CMAKE_INSTALL_LIBDIR
• Name the tools camerad-emulator, camerad-socksend and camerad-shm-reader, since emulator and socksend are too generic for a directory shared with every other package. camerad keeps its name
• Install the camera_interface Python module to lib, so it has a stable path to put on PYTHONPATH
• Don't install listener: nothing in camerad/ or common/ uses UdpSocket, so it has no producer to listen to
• Update the CI workflow and README to the new binary names
• Verify make install in CI: the python-module job now builds everything, installs to a prefix, checks all four binaries are present and executable, and imports the module from the prefix with the build tree off PYTHONPATH so a missing install rule cannot pass silently
• Verified locally by running open, load, power on, exptime 0, expose 1 against the emulator with only the installed binaries on PATH, all returning DONE, and by confirming the CI import assertion fails when pointed at the build tree