Multiview transform feedback now passes if the transform feedback is
paused. Also updates the relevant validation. This aligns the
ANGLE_multiview validation with OVR_multivew and with the WebGL
extension spec.

This change allow us to combine multiple draw call validation updates
into one update function.

Bug: angleproject:3012
Change-Id: I2ce04edc386039134198afa1792201e03cc20490
Reviewed-on: https://chromium-review.googlesource.com/c/1357148
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>