refactor: Implement the full copy-paste version to duplicate the layer builders

This follows the pattern where the type of input is pinned to the type of
memory and that is used to dispatch to the correct version of `build_rs` /
`build_attn`. There's a lot of code duplication that can hopefully be
pulled into common functions in the graph later.

Branch: GraniteFour

Signed-off-by: Gabe Goodhart <[email protected]>

Author: gabe-l-hart