Refactor and rework several areas of the Gradle plugin:
- Refactor package structure into functional areas and configure each
area separately via a new PluginFeatures interface.
- Convert BootRunTask to extend RunTask rather than attempting to
find existing RunTasks.
- Simplify agent integration by no longer needing specific BootRunTask
code.
- Update the repackage task to consider the `mainClassName` property
in addition to `springBoot.mainClass`.
- Automatically set `mainClassName` when calling `run` or `runBoot`
from `springBoot.mainClass` if there is one.
- Ensure that explicitly defined `main` options on JavaExec tasks always
take precedence.
Fixes gh-547, gh-820, gh-886, gh-912
794808b6b8