SandBox Workflow: Use theme colors in forms for PhoneInput and Button components

[dgolovin]

Some buttons and fields don't appear to be compatible with my dark theme, Dracula. See examples below:

Originally posted by @worldofgeese in #2474 (comment)

[dgolovin]

PhoneInput should look like Select components in VSCode Settings

Disabled Buttons should be shown as disabled buttons in view welcome page