Revert "Hide ICU C++ API from Skia users."

This reverts commit 5ef0d2f6c0ede86ecd67420ea1fe021bf3d36381.

Reason for revert: Sharing a build with flutter is crazy pants.

Original change's description:
> Hide ICU C++ API from Skia users.
> 
> Parts of third_party need the C++ API so hide it from Skia users as
> needed to prevent re-introduction.
> 
> This also avoids the ICU version renaming / name mangling when building
> our own test version of ICU. This makes life in an editor and debugger
> much easier.
> 
> Change-Id: I8fb1903e2b31e9dd04efa22173a03115d629c232
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/292854
> Reviewed-by: Julia Lavrova <jlavrova@google.com>
> Commit-Queue: Ben Wagner <bungeman@google.com>

TBR=bungeman@google.com,reed@google.com,jlavrova@google.com

Change-Id: If238225b20a6b73064e3b16c5e0bdc89760e522d
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/292966
Reviewed-by: Ben Wagner <bungeman@google.com>
5 files changed