Force texImage2D upload for videos

[bigtimebuddy]

Addresses #4089

This defaults texImage2D uploading instead of texSubImage2D for VideoResource objects.

See for more information and performance measurements: http://codeflow.org/issues/slow_video_to_texture/

Build:
http://pixijs.download/fix-video-performance/pixi.min.js

Example:
https://pixiplayground.com/#/edit/jpeAPzXpQFY336WzsTKqn (PR)
https://pixiplayground.com/#/edit/9vDVREwmsMLTMNoCgW2VI (5.1.3)

Measurements (Chrome 76)
I did a small benchmark in Chrome to see the performance. At least in Chrome, texImage2D is faster (although on my laptop I didn't perceive much of a different, would probably show up more on mobile/slower devices).

Branch	Duration	Render Time (lower is better)
5.1.3	5000ms	387ms texSubImage2D
fix-video-performance	5000ms	55ms texImage2D

[codecov-io]

Codecov Report

Merging #6088 into dev will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##              dev    #6088      +/-   ##
==========================================
+ Coverage   71.04%   71.05%   +<.01%     
==========================================
  Files         208      208              
  Lines       10624    10626       +2     
==========================================
+ Hits         7548     7550       +2     
  Misses       3076     3076

Impacted Files	Coverage Δ
...kages/core/src/textures/resources/VideoResource.js	75% <100%> (+0.21%)	⬆️
...s/core/src/textures/resources/BaseImageResource.js	93.93% <100%> (+0.18%)	⬆️

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[GoodBoyDigital]

nice! I have noticed this issue too, was hoping the browsers would step up and fix it b y now, but this will do the trick until they do 👍