Draft: Resolve "Nexus: Update to meet standards"

Big Bang merge request

Rename nexus key from .Values.addons.nexus to .Values.addons.nexusRepositoryManager
Maintains backwards compatibility by using a helm merge.

Package Changes

Nexus upgrade to 3.45.0

Package MR

https://repo1.dso.mil/platform-one/big-bang/apps/developer-tools/nexus/-/merge_requests/78

For Issue

Closes https://repo1.dso.mil/platform-one/big-bang/apps/developer-tools/nexus/-/issues/53