Revert "Rename LanguageCode and CLD3LanguageCode Enums"

This reverts commit a814d87a95200fda81f6daec4ba1541c913af350.

Reason for revert: CLD3LanguageCode enum is still referenced in ukm.xml and this CL breaks the server-side pipelines.

Original change's description:
> Rename LanguageCode and CLD3LanguageCode Enums
>
> This CL renames language code enums to make them more clear.
>
> The current enum |LanguageCode| hashes the first two letters of a local
> code and maps these to language name. This is renamed |LanguageName|.
>
> The current enum |CLD3LanguageCode| hashes the entire ISO639 locale code
> and maps these to the locale code.  This is renamed |LocaleCodeISO639|
>
> Bug: 1155031
> Change-Id: I08fce33d008e26af29607fe35f060c3800318d9a
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2613285
> Commit-Queue: Trevor  Perrier <perrier@chromium.org>
> Reviewed-by: Mark Pearson <mpearson@chromium.org>
> Reviewed-by: Megan Jablonski <megjablon@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#842708}

TBR=mpearson@chromium.org,tbansal@chromium.org,megjablon@chromium.org,chromium-scoped@luci-project-accounts.iam.gserviceaccount.com,perrier@chromium.org

Change-Id: If9165eb4ccde549503012d0b547fab9730ded55b
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1155031
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2625918
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Commit-Queue: Tarun Bansal <tbansal@chromium.org>
Commit-Queue: Alexei Svitkine <asvitkine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843172}