Multi-selection: Dynamic menu

[0nko]

Task/Issue URL: https://app.asana.com/0/72649045549333/1209118961868655

Description

This PR adds a dynamic menu that updates its menu items based on the selection view state.

Screen_recording_20250204_094857.mp4

The selection functionality isn’t implemented yet, so tapping on the FAB simulates different states.

1. Selection mode with no tabs selected
2. Selection Mode with 2 tabs selected
3. Normal (non-selection mode)

Figma screenshots for reference:

1.	2.	3.

The menu options don't do anything except for New Tab and Close All item.

Steps to test this PR

• Enable the tabManager / multiSelection feature flag in the settings
• Open the tab manager
• Notice the default menu reflects the Selection mode without selection (refer to 1.), with toolbar buttons disabled
• Tap on the FAB
• Notice the menu is updated to Selection mode with 2 tabs selected (refer to 2.), with toolbar buttons enabled and the number of tabs (2) reflected in the menu items
• Tap on the FAB
• Notice the menu is updated to Normal mode with the fire button and tab layout button (both working) and the correct menu (refer to 3.)

[0nko]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• Multi-selection: Dynamic menu #5588 👈 (View in Graphite)
• Multi-selection: Add new FAB to the tab switcher #5467
• Multi-selection: Add a new feature flag for multi-selection #5464
• develop

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