* `type_size_store` is no longer a thing. loading and storing a pointer
to a value may dereference up to `@sizeOf(T)` bytes, even for
integers such as `u24`.
* fix `types_have_same_zig_comptime_repr` to not think that the
same `ZigTypeId` means the `ConstExprValue` neccesarily has the
same representation.
* implement `buf_write_value_bytes` and `buf_read_value_bytes` for
`ContainerLayoutPacked`
closes#1120
3ee9d06cbd