Replace line-height() function with tokens

[alex-page]

Replace usage of the line-height() function with css custom properties according to the following scale.

Blocked by #4588 and #4600

'--lh-0': '16px',
'--lh-1': '20px',
'--lh-2': '24px',
'--lh-3': '28px',
'--lh-4': '32px',
'--lh-5': '36px',
'--lh-6': '44px',