Add inclusive time to HumanOutput

[Sharpie]

The human output format currently displays everything in terms of exclusive time -- that is time spent within a span after excluding time spent within child spans. For completeness, we should also display inclusive time, possibly with some highlighting similar to what explain.depesz.com does to emphasize spans where the bulk of execution time is spent:

• white background - is chosen if time <= 10% of total query time
• yellow background - is chosen if time ∈ (10%, 50%> of total query time
• brown background - is chosen if time ∈ (50%, 90%> of total query time
• red background - is chosen if time > 90% of total query time

Ref. https://explain.depesz.com/help