View / add a constrainResolution option

This introduces a breaking change.

This options replaces the various `constrainResolution` options on interactions
and the `fit` method.

Since constraints are now the responsibility of the View, the fact that intermediary
zoom levels are allowed or not is now set in the view options.

By default, the view resolution is unconstrained.

examples/interaction-options.js

@@ -7,7 +7,7 @@ import OSM from '../src/ol/source/OSM.js';
 
 const map = new Map({
   interactions: defaultInteractions({
-    constrainResolution: true, onFocusOnly: true
+    onFocusOnly: true
   }),
   layers: [
     new TileLayer({