Align verbose warnings (-Wconf / @nowarn) with Scala 3

[lrytz]

Once scala/scala3#12857 is merged:

• In -Wconf, remove the info-verbose / iv action, rename the warning-verbose / wv action to verbose / v
• Support @nowarn("verbose") in source code. Update the @nowarn annotation's Scaladocs.
• Improve the "verbose" warnings output to explicitly display the filters that match the warning (cat=deprecation, site=a.b.C, ...)

[dwijnand]

• In -Wconf, remove the info-verbose / iv action, rename the warning-verbose / wv action to verbose / v

Deprecate?

[SethTisue]

@lrytz is this a blocker for 2.13.7?

[lrytz]

Nah, I don't think so

[som-snytt]

Kicking the can down the road and unassigning to foster work stealing.

[lrytz]

I found that error-verbose would be very useful. When enabling fatal warnings in an existing project, it would be very helpful to see the verbose output in the new messages, to make it easier to write filters for some of them.