Update sidebar design

[ankormoreankor]

New design for the collapsed state of the Sidebar component

• Sidebar width in collapsed state is 62px; Collapse button moved to the sidebar body
• Sidebar on mobile screen width opens with the old approach - a button at topbar
• Sidebar legacy search bar is replaced with button in collapsed state
• New search bar is collapsed to the size of square button when sidebar is collapsed state
• New search bar is accessible from the keyboard now (can be activated with enter and space buttons)
• More menu and Settings menu behave as modals: close on click outside
• More, Settings and User Management menu items are accessible from keyboard now

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[sans-harness]

@ankormoreankor this PR completely breaks the MFE since we haven't wrapper the AppMFE in sidebar-provider. Also, changes to layouts - SandboxLayout, PRLayout etc are breaking layouts across pages in the MFE. As a result I am reverting some of the changes in this PR. Changes to layouts are usually dangerous and need more oversight before merging.

cc: @abhinavrastogi-harness @vardanbansal-harness