Checking sampler completeness after every sampler related
state change is inefficient. Defer sampler completeness
check to draw time.

Based on a CL by hckim.kim@samsung.com.

Bug: angleproject:4765
Tests: angle_perftests.exe --gtest_filter=TexturesBenchmark.*
Change-Id: I7e971371e40b3044ca3d5ca39bfe7fc600620c3e
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2268577
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Tim Van Patten <timvp@google.com>
Reviewed-by: Geoff Lang <geofflang@chromium.org>