update UI components

[Vanessa-Kris]

Updates:

• Threads pulsing loader (reduced size for sleeker look)
• Changed platforms tab icon (GridView icon does not have filled variant)
• Used displayname instead of platformname for selectaccount (displayname's first letter is capitalized or just capitalize the first letter of platformname)
• Updated primary color and removed dynamic color (the app ill always use our theme color)
• Updated last onboarding page to match figma design
• Made welcome screen button fullwidth
• Added color to compose button
• Moved relayalertdialog to top (compose button was blocking it).

[sherlockwisdom]

Removing dynamic color breaks the app on devices that support MaterialYou, are we sure that's the best case here? I will go along with it if we believe we don't need material you. It's something I use a lot