Scroll excluded term input fields into view when the bottom view insets change

[navaronbracke]

The inputs for excluded terms on the settings page (both the add term & edit term input) could use improved handling for avoiding the keyboard. Currently, only the edit excluded term field has some handling of this, but it does not always work.

We should investigate if we can hoist the view insets observing part out of the excluded term input fields.

When the excluded term input field calls its ensureVisible() implementation, it might be visible but behind the keyboard, which defeats the purpose of the method. Secondly, if the scrollable content does not include enough height to avoid the keyboard height, scrolling won't have any effect in certain cases.

Also remove the cached viewInsets in the input field.

[navaronbracke]

Something we can investigate is using maintainBottomViewPadding in a SafeArea widget together with resizeToAvoidBottomViewPadding. Essentially we need resizeToAvoidBottomViewPadding: true but on the list, not the scaffold