Replace global paths

We are deprecating and removing global paths from the elastic-agent-libs library

Even though apm-server is not affected, we would like to completely prevent this situation from re-occuring by completely removing the global accessors. Additionally, this is defensive against potential bugs occurring in the future. For example in https://github.com/elastic/apm-server/blob/1192ac741db23f774fa9cf07451da4906055568d/internal/beatcmd/beat.go#L140-L165 the paths object is not initialized in the Beat{} struct. Future changes in the beats repo could lead to accessing a nil pointer.

~~Blocked by https://github.com/elastic/beats/issues/49803~~