Release 2.0

[rickeylev]

Tracking issue for the 2.0 release

rc0

• Update change log, version markers chore: update changelog, version markers, for 2.0 release #3689
• Enable experimental_index_url by default
• Create 2.0 branch
• Tag 2.0.0-rc0

Final release

• Tag 2.0 final

[aignas]

I'd like to enable experimental index url by default in that release, so let me see if I can do something tomorrow. It should be a reasonably small change, so the diff won't be too invasive.