Remove JacocoFullReport task.

This plugin is no longer maintained and no longer works. It also tends to break the regular Jacoco reports. It was being used primarily as a premade JacocoMerge+Report task to feed a single report into SonarCloud but it makes more sense to just provide all three individual reports and let Sonar merge them. Where a coverage gate is desired for merged results in a local build, this can be considered a future feature.