feat(S2): add ActionBar support to TreeView

[reidbarber]

Adds ActionBar support to TreeView. Should be similar to TableView.

✅ Pull Request Checklist:

• Included link to corresponding React Spectrum GitHub Issue.
• Added/updated unit tests and storybook for this change (for new code or code which already has tests).
• Filled out test instructions.
• Updated documentation (if it already exists for this component).
• Looked at the Accessibility Practices for this feature - Aria Practices

📝 Test Instructions:

Check new stories and new docs.

🧢 Your Project:

[rspbot]

Build successful! 🎉

• View the storybook
• View the S2 storybook
• View the S2 docs
• View the React Aria docs

[rspbot]

Build successful! 🎉

• View the storybook
• View the S2 storybook
• View the S2 docs
• View the React Aria docs

[rspbot]

## API Changes

@react-spectrum/s2

/@react-spectrum/s2:TreeView

 TreeView <T extends {}> {
   UNSAFE_className?: UnsafeClassName
   UNSAFE_style?: CSSProperties
   aria-describedby?: string
   aria-details?: string
   aria-label?: string
   aria-labelledby?: string
   autoFocus?: boolean | FocusStrategy
   children?: ReactNode | (T) => ReactNode
   defaultExpandedKeys?: Iterable<Key>
   defaultSelectedKeys?: 'all' | Iterable<Key>
   dependencies?: ReadonlyArray<any>
   disabledBehavior?: DisabledBehavior = 'all'
   disabledKeys?: Iterable<Key>
   disallowEmptySelection?: boolean
   escapeKeyBehavior?: 'clearSelection' | 'none' = 'clearSelection'
   expandedKeys?: Iterable<Key>
   id?: string
   items?: Iterable<T>
   onAction?: (Key) => void
   onExpandedChange?: (Set<Key>) => any
   onSelectionChange?: (Selection) => void
+  renderActionBar?: ('all' | Set<Key>) => ReactElement
   renderEmptyState?: (TreeEmptyStateRenderProps) => ReactNode
   selectedKeys?: 'all' | Iterable<Key>
   selectionMode?: SelectionMode
   shouldSelectOnPressUp?: boolean
   styles?: StylesPropWithHeight
 }

/@react-spectrum/s2:TreeViewProps

 TreeViewProps <T> {
   UNSAFE_className?: UnsafeClassName
   UNSAFE_style?: CSSProperties
   aria-describedby?: string
   aria-details?: string
   aria-label?: string
   aria-labelledby?: string
   autoFocus?: boolean | FocusStrategy
   children?: ReactNode | (T) => ReactNode
   defaultExpandedKeys?: Iterable<Key>
   defaultSelectedKeys?: 'all' | Iterable<Key>
   dependencies?: ReadonlyArray<any>
   disabledBehavior?: DisabledBehavior = 'all'
   disabledKeys?: Iterable<Key>
   disallowEmptySelection?: boolean
   escapeKeyBehavior?: 'clearSelection' | 'none' = 'clearSelection'
   expandedKeys?: Iterable<Key>
   id?: string
   items?: Iterable<T>
   onAction?: (Key) => void
   onExpandedChange?: (Set<Key>) => any
   onSelectionChange?: (Selection) => void
+  renderActionBar?: ('all' | Set<Key>) => ReactElement
   renderEmptyState?: (TreeEmptyStateRenderProps) => ReactNode
   selectedKeys?: 'all' | Iterable<Key>
   selectionMode?: SelectionMode
   shouldSelectOnPressUp?: boolean
   styles?: StylesPropWithHeight
 }

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