This patch is the last one in the series of putting resource limits
on each shader stage into ShaderMap. With this patch, all such values
are organized in the corresponding ShaderMap.

This patch also cleans up all the related code by using this new
type of data structure.

BUG=angleproject:2169

Change-Id: I440643fe44ab63acf7da0a1611643beed1ba66d1
Reviewed-on: https://chromium-review.googlesource.com/1077748
Commit-Queue: Jiawei Shao <jiawei.shao@intel.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>