This updates all ICU4X crates and regenerates rustc_baked_icu_data.
Since the new unicode license under which they are licensed does not
have an SPDX identifier yet, we define some exceptions. The license has
to be reviewed to make sure it is still fine to use here, but I assume
that is the case.
I also added an exception for rustc_icu_data to the unexplained ignore
doctest tidy lint. This is a bit hacky but the whole style.rs in tidy is
a mess so I didn't want to touch it more than this small hack.
