web: update code-hosts `HoverOverlay` props

Created by: valerybugakov

Description

This the second preparation PR for the Code Intel redesign work. See the first one here.

Changes

• Changed iconButtonClassName to closeButtonClassName.
• Replaced infoAlertClassName and errorAlertClassName props with getAlertClassName prop. It's handy because in the redesign version we can easily add warningAlertClassName via getAlertClassName without introduction of a new component prop. Also, we can reuse notificationClassNames defined for each code-host to get the relevant alert class.
• Used notificationClassNames in code-hosts props to get relevant alert class.