Update browser for gnomAD v4

[nawatts]

Data pipeline

• Update version of GENCODE used in genes data pipeline #858
• Update MANE Select transcripts #859
• Create data pipeline for v4 variants #849
• Update version of VEP used in ClinVar data pipeline #851
• Use gnomAD v4 variants for annotation in ClinVar data pipeline #852
• Load v4 variants  #872
• Update liftover #876

API

• Implement GraphQL queries for v4 variants #850
• Extend variants schema with new fields added in v4 #861
• Decide what to do about dataset for STRs and mitochondrial variants #875

Browser

• Update components that render conditional on dataset (part 1) #853
• Update datasets menu #854
• Update browser's default dataset #860
• Update dataset metadata #855
• Handle requests for gnomAD versions that are no longer available #844

Documentation

• Update references to v3 in help and FAQ content #856

Reads

• Add v4 read data #857

[mattsolo1]

Converting this to a Zenhub epic #916. Didn't know how to do this without making a new issue.