mRAW support for Sony A7RV

Not being able open mRaw files from the Sony A7RV is preventing me from using Darktable as my main photo editing program, this requires me to use other programs like Captureone or Adobe Lightroom to edit these files which are not supported on Linux and also requires a copy of Microsoft Windows just to open these files.

adding support to this file format could allow more people to switch over to Darktable as their main photo editing program.

Sony mRAW is a medium-resolution RAW file format that captures images at 26 megapixels (on full-frame models like the a7R V and a7 IV) or 21 megapixels (in APS-C crop mode), offering smaller file sizes than full-resolution RAW while retaining raw data flexibility.
It is distinct from compressed RAW formats because it involves pixel binning or downsampling rather than just data compression, which can result in improved noise performance and reduced "grid" patterns at high ISOs.

Start by obtaining Sony A7RV mRAW files and reproducing the failure in darktable. Read the existing RAW import and camera-format handling before deciding where support belongs. Done means mRAW files from the Sony A7RV open successfully for editing on Linux without requiring Capture One, Lightroom, or Windows.