Revert "[lldb] Disable minimal import mode for RecordDecls that back FieldDecls"

This reverts commit 3bf96b03.

It causes crashes as reported in PR52257 and a few other places. A reproducer is bundled with this commit to verify any fix forward. The original test is left in place, but marked XFAIL as it now produces the wrong result.

Reviewed By: teemperor

Differential Revision: https://reviews.llvm.org/D113449