End to End testing for the publish plugin & clean-up of previously failed changes

[jdaugherty]

This change encompasses:

• not running publish action on forks
• not running the release notes action on fork (since secrets aren't available in forks / pull requests)
• end to end testing support for any gradle plugin in this project (including logging for tests in the action)
• added several tests for the publish plugin based on past issues
• publishes of a release using MAVEN_PUBLISH should sign the build
• added back the url validation when using maven publish (previously validation was happening at configure time which caused failures in assemble)
• add a warning when projectVersion is being used instead of project.version (longer term I think we may just want to make the release/snapshot determination an environment variable / system property instead of hard coded logic)
• updated some log statements to match the style of previous code review comments

This ticket does not fully fix #364 but it does help us diagnosis issues as they arise. There are 4 tests marked as pending feature which documents the issues found in #364. I think it may be reasonable that this can't be fixed, but I intend to investigate these further now that we have tests.

[jdaugherty]

This now supports build release/snapshot detection via environment variable too.