[number input] audit bugs

[laurenmrice]

• We need to change the caret controls to a plus and a minus. Here is the final design spec 5417
  
  

• There needs to be a 12px space between the control icons and the end of the field container.
  

• In Safari, the input text is the wrong color for the disabled state in the dark themes. Should be disabled-02.

• The mobile variant will be the same as the enabled state for the regular number input.
  

[emyarod]

#7687 will address the input controls overhaul, and after that is resolved we can deprecate the mobile input variant