Input field alert (error) on Environments form does not match default form validation

Found during color audit gitlab-design#289 (closed)

Operations > Environments > Edit/Create

Input field displays a floating alert when URL entered does not match visual state of the input field. This type of alert does not match the inline error implemented in different pages.

Icon color is also not safe for colorblind users.

Proposal

Replace form input with Form component from Pajamas, for built-in validation:

Error message: The URL should start with http:// or https://