Parent-Task:

• SR-10535 [stdlib] Drop ICU dependency

Issue Description:

As mentioned in https://forums.swift.org/t/icu-usage-in-swift/20473/7,

ICU includes a copy of the UCD and similar data. Accessing this is necessary to implement any of the other functionality ICU provides us as well as answer some APIs such as Unicode.Scalar.Properties, capitalization, etc. Accessing this data through ICU is typically too expensive for us to do in a hot-loop implementing one of the below algorithms, but is fine for public API.

This data is large and changes with every version of Unicode. Bundling this data in the standard library would require:

1. We prune out data we don't use
2. Find or invent a compact binary representation and lazy expansion mechanism
3. Vigilantly keep them up to date, tying versions of the standard library to specific Unicode versions.