Administration: Standardize form control height and alignment across the admin.

This improves the appearance of various form controls in the admin and addresses some visual inconsistencies in WordPress 5.3.

Props afercia, audrasjb, jameskoster, GDragoN, azaozz, michaelarestad, murgroland, SamuelFernandez, chetan200891, veminom, dlh.
Fixes #48420.
Built from https://develop.svn.wordpress.org/trunk@46866


git-svn-id: https://core.svn.wordpress.org/trunk@46666 1a063a9b-81f0-0310-95a4-ce76da25c4cd