Run unit tests workflow with vcpkg

[ranisalt]

Pull Request Prelude

• [x] I have followed proper The Forgotten Server code styling.
• [x] I have read and understood the contribution guidelines before making this PR.
• [x] I am aware that this PR may be closed if the above-mentioned criteria are not fulfilled.

Changes Proposed

Simplifies unit test setup using vcpkg to install dependencies. vcpkg has more up-to-date libraries than Ubuntu and is more consistent given that it will always install the same versions with an unchanged baseline commit.