Improve blocks style

[amjadr360]

This PR improves the style of the blocks and Grayscale style variation.

• Block post title: Remove text underline decoration and add hover, focus, and active state indicator.
• Block post terms: Remove text underline decoration and add hover, focus, and active state indicator.
• Block post date: Remove text underline decoration.
• Block query pagination numbers: Add spacing around numbers.
• Change headings font-weight for Grayscale style variation.
• Use normal font size beside medium for the search block button.