[ASTImporter] Modifying ImportDeclContext(...) to ensure that we also handle...

[ASTImporter] Modifying ImportDeclContext(...) to ensure that we also handle the case when the FieldDecl is an ArrayType whose ElementType is a RecordDecl

When we fixed ImportDeclContext(...) in D71378 to make sure we complete each
FieldDecl of a RecordDecl when we are importing the definition we missed the
case where a FeildDecl was an ArrayType whose ElementType is a record.

This fix was motivated by a codegen crash during LLDB expression parsing. Since
we were not importing the definition we were crashing during layout which
required all the records be defined.

Differential Revision: https://reviews.llvm.org/D86660