Refactor `StatusBar`

[ignas-k]

Is your feature request related to a problem? Please describe.

Currently our StatusBar is very messy and has some issues e.g. we have an internal FooterIndicator which can be inlined, we have public StatusBarIndicator which wraps public StatusBarField and StatusBarPopup components, StatusBarPopup uses old AppUI Popup which needs to be deprecated and replaced with iTwinUI Popover etc. The Popup usage causes problems because refactored status fields use the iTwinUI Popover so not all status fields open their popup with the same gap. Additionally, status bar overflow panel is broken because changing values in it doesn't work.

Describe the Solution you'd like

StatusBar needs a proper refactoring:

• We can probably deprecate StatusBar component because it only adds styling and nothing more (we use StatusBarComposer for content).
• Delete FooterIndicator and inline its content in StatusBarIndicator.
• The status bar overflow panel needs to be fixed.
• We need to look into if we need StatusBarField and StatusBarPopup.
• Deprecate AppUI Popup component.
• Generally investigate what else can be removed/deprecated/improved in StatusBar.