External deps in bazel might get a bunch easier as of Bazel 6

[h-vetinari]

Just got wind of bzlmod, which is available as a dependency specification as of bazel 6 (since early 2023).

In particular, we should be able to do something like

## MODULE.bazel
bazel_dep(name = "bazel_skylib", version = "1.4.2")
bazel_dep(name = "rules_java", version = "6.1.1")

together with a local_path_override, to be able to point to our own libs. 🥳

CC @conda-forge/tensorflow @conda-forge/bazel @conda-forge/core

Not 100% sure where to open this issue; I feel it's too niche for the main tracker and tensorflow is one of the heaviest users of bazel customisation, so I put it here.