TIMOB-13392: Android scrollable tabs

Android tab group can now by default be navigated by swipes (e.g. see Play Store app). The functionality can be toggled with the new `TabGroup.swipeable` property. In addition, tab navigation can be disabled (or re-enabled) by calling `disableTabNavigation(boolean)`. Plus added tab `selected` and `unselected` events (currently these events exist in Android only. In iOS the tab focus/blur events do the same - I suggest they be renamed to selected/unselected). Note that all additional events are fired exactly as before.
Yup, there's a good reason: as it turns out, in Android the Tab focus/blur events fire in many cases, not just when the tab is selected and unselected. For example - when the screen is locked/unlocked blur/focus will be fired (this is unlike iOS, BTW). So for clarity and also backwards compatibility, I did not touch the focus/blur stuff at all, but I did move relevant selection/unselection logic into the relevant events.
That's also why I added the selected/unselected tab events for Android. Again, the focus/blur events work exactly as before, so anything relying on them is not broken.