Mobs no longer suffocate inside of soul sand, farmland or grass paths

Clones MC-149928

In pre2 mobs became able to suffocate inside of soul sand again, as well as farmland and grass paths. However, this seems to have been removed again in pre3, likely as a fix for MC-166386 and MC-166389.

The suffocation should be readded again, but checking the mob's head height this time as to prevent erroneous silverfish suffocation. Suffocation could also be added to other solid blocks using this mechanic as per MC-134360.