Show validation warnings and errors on the map

[quincylvania]

Post-#5830, native iD issues are listed in a dedicated pane. We should show them on the map as well and have a visibility toggle like we have for KeepRight and ImproveOSM.

[BjornRasmussen]

I think that this is be a good idea if it isn't on by default, similar to how keepright errors are not on by default. If a new user is editing, and suddenly starts seeing a bunch of yellow warnings on the map, they will likely not know what they mean and why they are there. Turning on the map symbols should be a checkbox in the validations pane with default not toggled.

[quincylvania]

I think that this is be a good idea if it isn't on by default

Yep, this would be optional.

I'm also thinking that feature highlighting similar to iD's visual diffs (#6843) might be better than badges. There's lots of potential for different highlight styles. Re: #6616.