Align RM to the new Fluent Design

[vishwam]

Type of change?

• [ ] Bug fix
• [x] New feature
• [x] Enhancement
• [x] Breaking change (breaks backward compatibility)

Description, Context, Motivation

This PR is part of the effort to align IoT Central and RM to the new fluent design specified by our design team. Major changes:

• Switch color palette to that of Fluent CSS library
• Switch Select, Toggle, Tooltip, and a few other controls to the ones from the Fluent Controls library (Playground)
• Update input and grid styling to match that of the Fluent input/management list
• Switch to the Fluent Shell (Masthead + Global Navigation + Flyout integrated together for responsive behavior)
  • The documentation/help links are now moved to a flyout per design guidelines.
• Consolidate position of refresh bar
  • removed scrollbar customization
  • fix position of link on tiles
  • removed multiple loading on dashboard
• Use the light theme by default
• Change "Devices" tab to "Device Explorer", use icon from central.

For reference, here are two RM instances:

• Old
• New

Checklist:

• [x] All tests passed
• [x] The code follows the code style and conventions of this project
• [ ] The change requires a change to the documentation
• [ ] I have updated the documentation accordingly

This PR is a copy of https://github.com/Azure/pcs-remote-monitoring-webui/pull/1209, which was abandoned because the build agent doesn't work with PR from forks.

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