feat(maven): add support for ~/.m2/settings.xml in detectGlobalManagerSettings

[arldka]

Tell us more.

Currently, the use of the global .m2/settings.xml file is not supported by the maven manager.
It would be helpful to have a way to use the ~/.m2/settings.xml file or specify an inline settings.xml file in order to configure private repositories or mirrors for use in CI environments.

An implementation of this feature can be found on the following PR : #34716

It extends the existing GlobalManagerConfig and CustomExtractConfig already used by the npmrc and npmrcMerge attributes / config options that covers a similar ground but with the support for using the existing ~/.npmrc file in the npm manager.

[rarkins]

The current approach to npmrc is an antipattern that we don't wish to repeat, and is something we are looking to remove in future if possible. If Renovate supports 100+ package managers, we don't want 200+ manager-specific configuration options.

What information in a .m2/settings.xml file do you need to extract, and is there anything preventing you from configuring it in Renovate global config instead? i.e. is this requested for convenience, or do you think it's something you need?