This patch prepares for the `toHaveScreenshot` implementation
by splitting common parts from `toMatchSnapshot`.
Drive-by: fix default extension generation from `.bin` to `.dat`
for unknown buffers.
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
