Replace .reuse with rules_license

Currently, we are using .reuse to determine the license to our files. rules_license can be used to replace .reuse by providing Bazel rules for applying the licensing and propagating them through the build graph.

We should register our MIT license (LICENSES/MIT.txt) via the @rules_license//rules:license.bzl rule:

license(
    name = "license",
    ...
)

The license target should then be associated to all targets in the module in REPO.bazel

We have a done a similar thing in bazel/toolchain_utils