AoInput, AoSelect, AoTextarea, AoFileUpload: use aria-label when input label is hidden

# Issue summary

Currently you must provide labels for inputs, but have the ability to hide them. This was for accessibility reasons but it doesn't really actually get it right. display: none also hides text from screen readers. The correct way is to use aria-label, per https://www.w3.org/TR/WCAG20-TECHS/ARIA14.html

# Solution
For all these input components, put something that does this inside the input/select/textarea/whatever tag
```
If showLabel = false
aria-label="{{ label }}"
```

We could also just not render the `` element, and/or make this non mandatory. Won't really make a difference, so probably just preference.