VIDEO-7662: Publish snapshots to MavenCentral

[mmartikainen]

Description

JFrog no longer supports publication of snapshots. This PR provides the changes needed to publish audioswitch snapshots to MavenCentral instead. I also took the opportunity to refactor the Circle CI configuration a bit.

Breakdown

Gradle changes:

• remove references to artifactory
• publish snapshots to maven central snapshots repository
• remove obsolete jcenter from repositories

Circle CI changes:

• refactor Circle CI config file to use commands and executors
• add parameter for pre-release publishing to maven central
• add parameter for disabling default CI workflow
• add parameter and workflow for publishing a snapshot from any branch
• add comments and do other minor refactoring in CI config

Other changes:

• restore patch version number to 3, since that is the next version to be published
• update README with info on how to reference maven central snapshots
• add CHANGELOG entry
• add contributor

Validation

• Built locally
• CI builds are green
• Published a snapshot and validated that it can be consumed by following instructions in the readme

Additional Notes

I did not explicitly validate that publishing a release works as expected, however that will happen after this PR has been merged.

Submission Checklist

• [x] The source has been evaluated for semantic versioning changes and are reflected in gradle.properties
• [x] The CHANGELOG.md reflects any feature, bug fixes, or known issues made in the source code

[rpanadero]

What is ETA? I'm waiting for the new release that supports Android 12 devices. Thanks.