Calcite-components: [calcite-input] Add prop to disable component

[jcfranco]

Currently, there is no way to disable inputs without custom code.

cc @macandcheese

[macandcheese]

Roger 🤙

[macandcheese]

Thoughts on having a disabled prop on calcite-label in addition to one on calcite-input that could be inherited by calcite-input but also by any wrapped controls?

If so should there by a styling adjustment for disabled items (would need to be distinct from readOnly)... Probably our 0.4 opacity treatment we use everywhere else with pointer-events:none will work.

[jcfranco]

My 2 cents: I wouldn't expect label to have a disabled prop.