Release Arrow `20.0.0` (next release after `19.0.0`)

[alamb]

• Planned Release Candidate: 2022-08-05
• Planned Release and Publish to crates.io: 2022-08-08

Items:

• Update version to 20.0.0 and update CHANGELOG #2323
• Create release candidate: https://lists.apache.org/thread/5cgwzomx82l7x0xkm7jnw5x5jbs0kg3d
• Release candidate approved
• Release to crates.io
• Draft update to DataFusion: Upgrade to arrow 20.0.0 datafusion#3007 (thanks @stuartcarnie and @avantgardnerio !)

See full list here:
19.0.0...master