Multiple Maven Repositories

**What would you like to be added**:

syft can authenticate and communicate with multiple maven repositories for its networking features

**Why is this needed**:

currently you can only configure one `maven-url` in the syft settings and the maven reposistory can't be authenticated against.

**Additional context**:

When using private registries or parent poms you reach the point of multiple repositories quite fast (unfortunately!). I think the best would be to leverage the current authentication mechanism of the package managers itself but are also open to configure each url and a password.

No files or tests are named. Start by locating the current `maven-url` setting and the existing package-manager authentication mechanism, then trace how Maven repositories are contacted for parent POMs and private registries. Done means configuring multiple Maven repository URLs and authenticating against them, with behavior covered for the stated use cases.

Written by the indexing model from the issue text.