Consolidate Chromium

[o-t-w]

Because Microsoft Edge is a popular browser and there are occasionally minor differences with Chrome (e.g. Edge didn't support AVIF images for ages), it probably makes sense to continue to list it seperately. However, other Chromium browsers are neither different enough nor significant enough to justify their own entry. Maintaining seperate data for more browsers makes contribution harder. There are dozens of browsers based on Chromium (Arc, Brave, Vivaldi, Opera, etc). I'm a user and fan of both Arc and Brave but as a developer it makes it harder to scan and assess the data when barely-distinguishable browsers are listed seperately.
I suggest that data for Opera desktop is removed and the following issues are closed #2964 #2749

In the course of my whole career I have never heard a stakeholder or developer ask about Opera support.

[HM100]

IIRC, both Opera and Edge were initially begun as non-chromium browsers before becoming such. Edge became Chromium-based since 2020