Merge compose.desktop.application plugin with compose plugin

This change removes `org.jetbrains.compose.desktop.application` plugin id
in favor of doing everything in `org.jetbrains.compose`.
The change simplifies configuring Compose Desktop projects.
Now, just one plugin dependency is needed.

To avoid task name conflicts with common task names such as `package` and `run`,
the plugin creates tasks lazily only if `application` block/property is used in a script.