* fix(toolbar): accessibilityLabel should be translatable.

This commit adds a helper property to get the accessibilityLabel of an item,
providing a translation if one is available. This mimics the behavior of
label and tooltip.

* fix(toolbar) 'hangup' button accessibilityLabel i18n

* fix(toolbar) 'mute' button accessibilityLabel i18n

* fix(toolbar) 'videomute' button accessibilityLabel i18n

* fix(toolbar) 'moreActions' button accessibilityLabel i18n

* fix(toolbar) 'shareRoom' button accessibilityLabel i18n

* fix(toolbar) 'audioRoute' button accessibilityLabel i18n

* fix(toolbar) 'toggleCamera' button accessibilityLabel i18n

* fix(toolbar) 'audioOnly' button accessibilityLabel i18n

* fix(toolbar) 'roomLock' button accessibilityLabel i18n

* fix(toolbar) 'pip' button accessibilityLabel i18n

* fix(toolbar) 'invite' button accessibilityLabel i18n

* fix(toolbar) 'raiseHand' button accessibilityLabel i18n

* fix(toolbar) 'chat' button accessibilityLabel i18n

* fix(toolbar) 'shareYourScreen' button accessibilityLabel i18n

* fix(toolbar) 'fullScreen' button accessibilityLabel i18n

* fix(toolbar) 'sharedvideo' button accessibilityLabel i18n

* fix(toolbar) 'document' button accessibilityLabel i18n

* fix(toolbar) 'speakerStats' button accessibilityLabel i18n

* fix(toolbar) 'feedback' button accessibilityLabel i18n

* fix(toolbar) 'shortcuts' button accessibilityLabel i18n

* fix(toolbar) 'recording' button accessibilityLabel i18n

* fix(toolbar) 'settings' button accessibilityLabel i18n

* fix(welcomepage) accessibilityLabels i18n

* fix(toolbar) 'info' button accessibilityLabel i18n

* fix(i18n): Add translation to various aria-label property values.

* fix(i18n): Differentiate between overflow menu and button.

Contributing all buttons in one place goes against the designs that we
set out at the beginning of the project's rewrite and that multiple of
us have been following since then.

Use the new abstractions, which already take care of the rendering part.

To be consistent with how the main window toolbar has audio mute,
hangup, and then video mute.