[LLDB] Close previously opened handles in `PseudoConsole` (#176775)
In
https://github.com/llvm/llvm-project/pull/175837#issuecomment-3749408432
I mentioned that any handles that were previously opened and haven't
been closed since, won't be closed in the destructor nor in
`OpenPseudoConsole`.
In this PR, I added `Close` calls to these methods. Calling `Close()` is
a no-op if the handles are invalid.