Omnibar position: Bottom app bar layout

[0nko]

Task/Issue URL: https://app.asana.com/0/1207418217763355/1207988999525948/f

Description

This PR implements the bottom omnibar layout, including the hide animation on scroll. The position of the omnibar is determined based on the setting stored in the shared preferences.

Steps to test this PR

• [ ] Go to Settings -> Appearance -> Address bar
• [ ] Change the position selection and tap Save
• [ ] Go back to the browser screen
• [ ] Notice the screen is reloaded with the omnibar repositioned
• [ ] Try scrolling and notice the omnibar is hidden/shown
• [ ] Repeat the steps above with the other position option

UI changes

https://github.com/user-attachments/assets/edfad444-e6df-4bee-bcd8-81cfe6d0e4f1

[0nko]

• #4939
• #4930 👈
• #4886
• #4885 : 4 other dependent PRs (#4940 , #4941 , #4974 and 1 other)
• develop

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