feat(tab): add persistentTabBar option for keep the tab pinned

[usmanvrtx]

Summary

Add persistentTabBar support so the tab bar stays pinned while only the tab content scrolls.

Key Changes

TabBar Behavior

• Add persistentTabBar parameter to TabBar.
• Keep the tab bar fixed at the top.
• Scroll only the selected tab content.

Usage

  body:
    TabBar:
      styles:
        persistentTabBar: true

[TheNoumanDev]

We are wrapping it with Expanded widget based on persistentTabBar, and also wrapping it with Expanded when isExpanded is also true, so if we set both properties, it gets wrapped twice in Expanded widget. Can you check if using both properties breaks it or works fine?

Verify with some edge cases:

• persistentTabBar: true + content has ListView
• persistentTabBar: true + content has Expanded child
• Tab content shorter than the screen, verify that it takes space as widget space or it takes extra space.