Make fields/parameter names more clear

[LukaszKontowski]

There are some confusing / unclear parameter names in the source code. For example:

final case class DependencyProvider(
    intelliJ: IntelliJDependencyProvider,
    plugin: PluginDependencyProvider,
    jbr: JbrDependencyProvider
)

Where we have plugin: PluginDependencyProvider and later on we have following method call in the code:
val file = dependencies.plugin.fetch(plugin)
Where first plugin refers to the PluginDependencyProvider type and second one to an object of Plugin type. There are more cases like this one. We should rename such fields / parameters for better code readability.

[PawelLipski]

Note that we need to be considerate wrt. backward compatibility of the HOCON config when doing any such renames 🤔

[LukaszKontowski]

Sure, special care for parameter names used by the IdeProbeConfig and its fields.