TLDR;

What this PR does is:

1. In modulejava.startup.mason-dep: extracts the code responsible for adding custom registries to Mason frominstall into a separate functionadd_custom_registries.

2. In modulejava: callsmason-dep.add_custom_registries prior tostartup_check insetup

Longer explanation:

Pt. 1 is necessary becausestartup_check needs to be called beforemason-dep.install injava.setup but alsomason-dep.install was adding the registries, so the verification was always going to fail. It allows formason-dep.add_custom_registries to be called independently.

Pt. 2 is necessary because custom registries need to be added before the invalid registry verification for it to succeed.

fixes#403