Revert "Fix defines for icu_subset"

This reverts commit 6dc1544c997bc7ec1366b76cd4dc22bf359d0298.

Reason for revert: Breaking CMake and Windows Shared

Original change's description:
> Fix defines for icu_subset
>
> Disabling the version suffix, but not supplying a lib suffix
> caused the ICU headers to try to re-define the "icu" namespace.
>
> This reworks the skunicode BUILD.gn rules to isolate the ICU
> specific defines that were causing issues. We now have several
> builds of skunicode that get bundled together (much like how
> the Bazel build works).
>
> This also fixes the plain text editor application, which was
> not using ICU/Harfbuzz as expected.
>
> Change-Id: Ia15dc9ad5d1da826608e6b4f9a137009fb5ed6bc
> Bug: b/40045064
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/833798
> Reviewed-by: Ben Wagner <bungeman@google.com>

Bug: b/40045064
Change-Id: I8337eeb430df414467aad569df68c55bb40d934a
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/834818
Auto-Submit: Kevin Lubick <kjlubick@google.com>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
9 files changed