replace macOS encrypted image on macOS 11+

[sweetppro]

various discussions on this... most recent is here:
closes #3217

[sweetppro]

here's a screen from macOS Monterey

[GaryElshaw]

Colour; and other code changes in that xib

[ckerr]

Just out of curiosity, on what platforms will this be supported and which will it be not supported?

[sweetppro]

Just out of curiosity, on what platforms will this be supported and which will it be not supported?

the new system icon will be shown on macOS11+, otherwise the older png file will be shown

[GaryElshaw]

Just out of curiosity, on what platforms will this be supported and which will it be not supported?

the new system icon will be shown on macOS11+, otherwise the older png file will be shown

@sweetppro @ckerr Merge mine then this immediately after?

[ckerr]

Approving since this seems to match all the discussion in the other threads.

If anyone doesn't speak up to request changes, I'll merge this tonight

[GaryElshaw]

If i wanted to change the colour locally, how do i do that @sweetppro?

[NSImage systemSymbol:@"lock.fill" withFallback:@"Lock"] : nil;

@sweetppro ping

[GaryElshaw]

Can these be taken down by a couple of pixels and centred? Note how they don't float in the middle but sit on the line.