Prepare for 20.0.0 release [Part 1]

[andygrove]

Which issue does this PR close?

N/A

Rationale for this change

Time for scheduled release

What changes are included in this PR?

• Change version to 20.0.0
• Update release script for new execution crate
• Update release script for changes to use version = { 'workspace' = true }

I cannot generate the changelog due to #5549 and will follow up with a separate PR once I find a solution

Are these changes tested?

Are there any user-facing changes?

[avantgardnerio]

LGTM!

[ursabot]

Benchmark runs are scheduled for baseline = 8b5c1c7 and contender = a768004. a768004 is a master commit associated with this PR. Results will be available as each benchmark for each run completes.
Conbench compare runs links:
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on ec2-t3-xlarge-us-east-2] ec2-t3-xlarge-us-east-2
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on test-mac-arm] test-mac-arm
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on ursa-i9-9960x] ursa-i9-9960x
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on ursa-thinkcentre-m75q] ursa-thinkcentre-m75q
Buildkite builds:
Supported benchmarks:
ec2-t3-xlarge-us-east-2: Supported benchmark langs: Python, R. Runs only benchmarks with cloud = True
test-mac-arm: Supported benchmark langs: C++, Python, R
ursa-i9-9960x: Supported benchmark langs: Python, R, JavaScript
ursa-thinkcentre-m75q: Supported benchmark langs: C++, Java