Add timing customizations to the advanced cohort tabs

[samjaros-stanford]

Mirroring the main timing tab, each cohort should get a timing section in their advanced tab that allows users to customize how the intervention timings work

• UI should draw timing section in the advanced cohort tabs
• Timings by cohort should default to values from the main timing section
• Study configuration should handle timings changing by cohort
• Study assembler should handle timings changing by cohort