Fix invalid results for Opera Mobile

[steverep]

Fixes #766 by:

• Remove use of Opera desktop when using mobileToDesktop: true as the release history is quite different
• Adds logic similar to Android to handle the CanIUse version jump from 12.1 to latest
• Removes unused mapVersions function
• Adjusts existing tests and adds one to test handling the version jump for "last" queries
• Removes aliasing version 59 to 58 (both of these versions exist but cannot be selected anymore anyway)

Note that neither the android nor op_mob jumps are handled perfectly when querying only "major" versions, but that's truly an edge case. I can follow up later with a fix for that.

[ai]

Looks very nice.

Do you need to release it now?

[steverep]

No rush to release if you're waiting on something else. My end goal is getting a regex for serving modern/legacy builds that is not overly restrictive on mobile. I think I'm good with this repo for now and need to work on browserslist/browserslist-useragent-regexp#1484.

[ai]

Released in 4.21.9.