Move WebGLStateTracker files to the same location as the rest of WebGL.
<rdar://problem/104721662>
Pull request: https://github.com/WebKit/WebKit/pull/9198
Committed 259469@main (5dc808f284eb): <https://commits.webkit.org/259469@main> Reviewed commits have been landed. Closing PR #9198 and removing active labels.