Fixes MNG-5663 - a regression introduced in 3.2.2 by MNG-5639 that prevents nested import POMs from resolving their dependencies.

The cuplrit was the resetRepositories method in tandem with the repository
list instances being shared between ModelResolvers.

- The copy constructor for the ModelResolvers now creates new lists.
- The resetRepositories method has been removed. Instead there is a
'replace' parameter on the addRepository method that allows the
desired parameter replacement of MNG-5639 to take place.

Signed-off-by: Jason van Zyl <jason@tesla.io>