Get rid of the double config nesting

[sschuberth]

          Note to myself: Let's [discuss later](https://github.com/oss-review-toolkit/ort/wiki/Kotlin-Developer-Meeting#2023-10-30) if this class could be inlined to get rid of the double `config` nesting.

Originally posted by @sschuberth in #7690 (comment)

[sschuberth]

Due to the recent refactoring, this now requires rather ugly constructs like

ortResult.scanner?.config?.config?.get("DOS")?.options?.get("frontendUrl")

The proposal is to either "inline" the nested config by moving it one level up, or to rename it to e.g. plugins, so it would read

ortResult.scanner?.config?.plugins?.get("DOS")?.options?.get("frontendUrl")

/cc @Etsija

[mnonnenmacher]

I would be in favor of renaming config to plugins. In addition I would suggest to add helper functions that make it easier to get the plugin configuration especially from scripts like the evaluator rules. Some ideas:

ortResult.getPluginConfig<ScannerWrapper>("ScanCode"): PluginConfiguration?
ortResult.scanner.getPluginConfig("ScanCode"): PluginConfiguration?
ortResult.scanner.getScannerWrapperConfig("ScanCode"): PluginConfiguration?

[sschuberth]

I would be in favor of renaming config to plugins.

Yeah, I also believe the name makes sense as the values in that map are always of type PluginConfiguration.