Move everything to the com.squareup.workflow1 package for release

[zach-klippenstein]

• Slack discussion
• Another, internal slack discussion

[zach-klippenstein]

On argument against doing this is that it's going to make it very difficult to merge changes between 1.x and 2.x development branches in the future, since those files will all be in different locations.

[zach-klippenstein]

Jake pointed me to https://jlbp.dev/JLBP-6, which also links to https://jakewharton.com/java-interoperability-policy-for-major-version-updates/.

Separate maven group ID and package name seem like the right move. We can either change the pre-release name, or the 1.0 name. Since changing the pre-release name requires doing a large rename PR internally before we can update, which is going to be almost impossible, and also since the current version is already pretty much a solid version in its own right, we've decided to rename the Maven artifacts' groups and package names to com.squareup.workflow1.