Enable testing of CLDR and ICU pre-releases

[sffc]

We should be able to point to an arbitrary tag in CLDR and/or ICU and add it to the dashboard.

[sffc]

Specific deliverables:

1. Make a way to pull ICU4J from the maven artifact CI job
2. Need to investigate how to get it for ICU4C
3. For ICU4X, we can just install from a git tag, because cargo supports that very well
4. For CLDR, we already build from a local checkout.

The version name in the dashboard can be called anything arbitrary, perhaps "icu78-dev".