[lldb-vscode] Use auto summaries whenever variables don't have a summary (#66551)

Auto summaries were only being used when non-pointer/reference variables
didn't have values nor summaries. Greg pointed out that it should be
better to simply use auto summaries when the variable doesn't have a
summary of its own, regardless of other conditions.

This led to code simplification and correct visualization of auto
summaries for pointer/reference types, as seen in this screenshot.

<img width="310" alt="Screenshot 2023-09-19 at 7 04 55 PM"
src="https://github.com/llvm/llvm-project/assets/1613874/d356d579-13f2-487b-ae3a-f3443dce778f">