Changes the types of `std.builtin.Type` `name` fields from `[]const u8`
to `[:0]const u8`, which should make them easier to pass to C APIs
expecting null-terminated strings.

This will break code that reifies types using `[]const u8` strings, such
as code that uses `std.mem.tokenize()` to construct types from strings
at comptime. Luckily, the fix is simple: simply concatenate the
`[]const u8` string with an empty string literal (`name ++ ""`) to
explicitly coerce it to `[:0]const u8`.

Co-authored-by: Krzysztof Wolicki <der.teufel.mail@gmail.com>