Most of this migration was performed automatically with `zig fmt`. There
were a few exceptions which I had to manually fix:
* `@alignCast` and `@addrSpaceCast` cannot be automatically rewritten
* `@truncate`'s fixup is incorrect for vectors
* Test cases are not formatted, and their error locations change
These are unused in LLVM, but in gcc used for example by rl78.
Move test files into common file, add tests for aforementioned routines
and missing ones for __lshrti3.