Fix: Add shading to river slopes

Adds a 32bpp shading to the river rapids/slopes to make them more visible. Requires a bump of original graphics grfs to use container version 2. Fixes #9031

Change: When building NewGRFs, use grfid (from grfcodec) to calculate NewGRF MD5 hash. (#11492)

This allows for v2 container NewGRFs to be created. Hashes are needed for building the baseset metadata, so the .hash files are stored the source tree so they can be built if grfcodec and grfid are not present.

The hash of openttd.grf is not actually needed, but it is simpler to leave it in than handle only orig_extra.grf.