Remove UCSC header and UCSC footer from theme

[knice]

• [x] The global header and global footer in the UCSC 2022 WordPress theme should not be editable by site owners.
• [x] The global header and global footer should be able to get updated on all sites at the same time, and independent of the theme.
• [x] Global header and global footer HTML/CSS/Javascript should be available to web developers outside of the WordPress environment.