Fix map pan when touchZoom is disabled

[cherniavskii]

Fixes #5779, closes #5951.

In #4552 @perliedman introduced change, which allows page native scroll when the touch zoom and map drag handlers are disabled.
How it works on current master:

dragging	touchZoom	Result
enabled	enabled	✅ dragging and touchZoom work
disabled	disabled	✅ neither dragging nor touchZoom work, page is not prevented from scrolling
disabled	enabled	✅ dragging doesn't work, touchZoom works, page is not prevented from scrolling
enabled	disabled	⚠️ touchZoom doesn't work, but dragging doesn't work either, page is not prevented from scrolling. Expected: touchZoom doesn't work, dragging works and page is not prevented from scrolling - #5779

So touch-action: none should be added if dragging is enabled and should not be added if dragging is disabled, whether touchZoom is enabled or not.

[cherniavskii]

Looks like modified CSS rule can be combined with that above, but I'm not sure which -ms-touch-action value should stay.
Also, I haven't tested it on Edge/IE, I'll appreciate any help with that.
Added touch-action: pinch-zoom, since it's already supported in Chrome 56+ and a fallback touch-action: none for FF.

[perliedman]

👍 Nice, sorry for taking forever to review/merge. Just can't find that much time for Leaflet these days 😢

[cherniavskii]

@perliedman no worries :)