[FIXED JENKINS-17680] Added a code to migrate from Copy Artifact < 1.26.

When upgrading Copy Artifact plugin from version < 1.26 to version >= 1.26, projectName fields are erased. It is so irritating when many projects are configured with Copy Artifact plugin.

That is caused for 6243f6bcd5ebe872d3c03c8d740b45e3d714f1c4, which split `projectName` into `project` and `parameters` .

This request does followings:
* Add tests to verify JENKINS-17680. Bundled a job configuration saved with Copy Artifact 1.25.
* `CopyArtifact#readResolve` does migration.