This patch pulls `expect.toHaveScreenshot()` from 1.20 release.
We'd like to experiment more.
After this patch, there is no 'toHaveScreenshot' mention in the
codebase.
This patch adds additional options to `toMatchSnapshot` method:
- `pixelCount` - acceptable number of pixels that differ to still
consider images equal. Unset by default.
- `pixelRatio` - acceptable ratio of all image pixels (from 0 to 1) that differ to still
consider images equal. Unset by default.
Fixes#12167, #10219
