Update browser for gnomAD v4 (checklist)

[mattsolo1]

Converting https://github.com/broadinstitute/gnomad-browser/issues/848 into a Zenhub epic.

Data pipeline

Genes

• [x] #858
• [x] #859
• [x] #1168

Coverage

• [x] #1180

Variants

• [x] #849
• [x] #1181
• [x] #1179
• [x] #851
• [x] #852
• [x] #872
• [x] #876

Infrastructure

• [x] #1182
• [x] #1183

API

• [x] #850
• [x] #861
• [x] #875

Browser

• [x] #853
• [x] #854
• [x] #860
• [x] #855
• [x] #844
• [x] #1184
• [ ] #1185

Documentation

• [x] #856
• [x] #1165

Reads

• [x] #857