fix(css): rename display mixins to match naming conventions

• Re #1090 (closed)
• Closes #982 (closed)
• Integration MR: gitlab!51918 (merged)

What does this MR do?

This renames responsive display utilities to match our naming conventions.

• gl-display-sm-none -> gl-sm-display-none
• gl-display-md-none -> gl-md-display-none
• gl-display-lg-none -> gl-lg-display-none
• gl-display-sm-flex -> gl-sm-display-flex
• gl-display-md-flex -> gl-md-display-flex
• gl-display-lg-flex -> gl-lg-display-flex
• gl-display-sm-inline-flex -> gl-sm-display-inline-flex
• gl-display-lg-inline-flex -> gl-lg-display-inline-flex
• gl-display-sm-block -> gl-sm-display-block
• gl-display-md-block -> gl-md-display-block
• gl-display-lg-block -> gl-lg-display-block
• gl-display-lg-inline-block -> gl-lg-display-inline-block
• gl-display-lg-table-cell -> gl-lg-display-table-cell