Implement BitmapData.copyPixels()

[torokati44]

This adds the main content (left-scrolling foreground image) to z0r.de/7463, solving another third of #2073.
This should also help with #2240, although other missing features seem to block this from making any difference there.

I tried to test this implementation with a variety of different parameter sets, using this test script: BitmapCopyPixels.as

Which produces this image in the Adobe player:

There is at most 1 value of difference from this in any channel of any pixel when run in Ruffle, as shown in this exaggerated difference image:

These are most likely rounding errors or other slight imprecisions. I don't find these to be too big of an issue.
The output is visually exactly the same, at least to my eyes.

[Toad06]

Also fixes graphics in Super Chick Sisters, making the game playable. 👍

[torokati44]

Now that I'm looking more closely, some subpixels might differ by more than 1. Oh well, it's still not noticeable.

[Herschel]

Thanks! Accuracy could be improved later.

[actinetwork]

This is a case for copyPixels() function that does not render the same result in a game.
Link to the SWF: https://files.acticdn.com/278374/2678/2678.swf
I have almost the same issue in this game too: https://files.acticdn.com/278374/2889/2889.swf

The screenshot from Flash Player:

The screenshot from Ruffle:

Hope this help you.

[torokati44]

Playing 2678.swf I see a gigantic batch of BitmapData.draw - not yet implemented warnings on startup. This is a more likely cause of the missing graphics. The bitmaps serving as source for copyPixels are probably left empty instead of being drawn upon.
See: #290, and related: #2240, #3193, #3721

And checking in Flash Player what 2889.swf is supposed to look like, it appears to be because of the missing blend mode support. See: #58, and related:#929, #3061