[lldb] Add missing debugserver dependency to check-lldb

D96202 removes the test dependency on debugserver which is causing a bunch of
tests to fail on a clean build.

This patch re-adds the dependency. I decided to not add the dependency in the
`test/API` folder as we actually need it in all kinds of tests (we have shell,
API and a few unit tests such as the LLDBServerTests that depend on the
debugserver binary). lldb-server is also handled in the same way.

Reviewed By: JDevlieghere, labath

Differential Revision: https://reviews.llvm.org/D98196