Drop "Z" encoding for "BOOL", use "B" (bool) instead #11
Description
All currently supported platforms (arm64 and x86_64) use the same representation for BOOL and bool. Hence the separate "Z" encoding for BOOL is no longer necessary.
The separate encoding was introduced because the two aren't the same for PowerPC (32-bit), but that platform hasn't been supported in a long while.
Note that we still have to generate metadata overrides for argument/return values of type "BOOL" because the standard encoding for that is the same as char.