Implications of hiding implementation details from .swiftmodule files on LLDB

Hi all. In Policy on hiding implementation details from Swift module interface, I discussed the implications of removing private declarations from .swiftmodule files on diagnostics. I've been working more towards this, but have come across changes that indicate LLDB may impose some requirements. I've come across this PR: [Serialization] Prepare the infrastructure for the deserialization safety feature by xymus · Pull Request #62886 · swiftlang/swift · GitHub. It introduces a kind of "poison" ...