Follow-up of the cl, implementing fmamebuffer parameters api
(https://chromium-review.googlesource.com/c/412126/). Moving entry point
function FramebufferParameteri and GetFramebufferParameteriv to context
according to Jamie's commemts.

BUG=angleproject:1594
TEST=dEQP-GLES31.functional.state_query.framebuffer_default.framebuffer_default*

Change-Id: Ib8a286afe97716576cf5d0a5338eee6588a4e25c
Reviewed-on: https://chromium-review.googlesource.com/444283
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Yunchao He <yunchao.he@intel.com>
Reviewed-by: Geoff Lang <geofflang@chromium.org>