feat: vendir manager

[dominik-bln]

Changes

Adds a very basic vendir manager, initially only with the ability to update dependencies of the helmChart type.

Context

• #17711

Documentation (please check one with an [x])

• [ ] I have updated the documentation, or
• [ ] No documentation update is required

How I've tested my work (please select one)

I have verified these changes via:

• [ ] Code inspection only, or
• [x] Newly added/modified unit tests, or
• [ ] No unit tests but ran on a real repository, or
• [ ] Both unit tests + ran on a real repository