Move the core standard library to the installation.

[chandlerc]

This removes the data_dir from the driver favoring the installation abstraction for the both locating the prelude and linking utilities.

With this, an installed toolchain should also be able to compile and link Carbon successfully, and the build of the examples should exercise this path almost exactly. (The only difference is using the driver cc_binary directly rather than relying on the symlink from inside the install tree.)

Note, depends in #3994 -- only the last commit should be reviewed here.