This updates our local ICU overlay port to use ICU 76.1. This includes
Unicode 16 and CLDR 46.
Upstream vcpkg is not able to supply versions past 74 yet due to various
dependency issues, but we are able to use this version ourselves. The
overlay port now includes a patch to revert ICU's dependence on autoconf
2.72 for now, as this version is not yet available on all systems.
All of the test changes were cross-referenced with Firefox to ensure
correctness.
In ICU 76, the default was changed from "arab" to "latn". See:
c149724509
The whole point of these tests was to use a non-Latin numbering system.
This patch ensures that is the case to make following patches easier to
grok.
