[web] Fix drawImage colorFilter with dstATop blend mode

[ferhatb]

• Changes dstATop color filter handling with drawImage api to use svg feCompositeBlendMode instead of background-blendmode for correct porter-duff handling.
• Refactor: Moved test flutter log image into separate file.

Related issue: flutter/flutter#76966
Related golden update: flutter/goldens#185

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[mdebbar]

@ferhatb I think you reverted the goldens_lock change by mistake in the last merge commit.