Update header styles and components to use uswds 3

[nick-mon1]

Summary

Updates header styles to use uswds:

• color tokens
• font tokens
• usa-select component

Note
Site wide styles are still using uswds 0.9 and will be removed as each section gets updated to 3.0

Screenshots

Current

New

Current colors:

$red: #981b1e;
$light-blue: #0071bc;
$light-blue-two: #2b75b9;
$dark-blue: #112e51;
$light-gray: #f9f9f9;
$uswds-light-gray: #aeb0b5;
$gray: #e4e4e4;
$dark-gray: #323a45;
$white: #fff;

New USWDS colors:

$red: color("red-70v");
$light-blue: color("blue-50v");
$light-blue-two: color("blue-50");
$dark-blue: color("blue-80v");
$light-gray: color("gray-2");
$uswds-light-gray: color("gray-cool-30");
$gray: color("gray-10");
$dark-gray: color("gray-cool-70");
$white: color("gray-1");

This pull request is ready to merge when...

• Tests have been updated (and all tests are passing)
• This code has been reviewed by someone other than the original author
• The change has been documented