[LLDB][NativePDB] Forcefully complete a record type if it has empty debug info...

[LLDB][NativePDB] Forcefully complete a record type if it has empty debug info and is required to have complete type.

It's required in following situations:
1. As a base class.
2. As a data member.
3. As an array element type.

Reviewed By: labath

Differential Revision: https://reviews.llvm.org/D134066