[lldb] Fallback to expression eval when Dump of variable fails in dwim-print (#151374)
Previously, when dwim-print finds a frame variables, it returns immediately after
calling `Dump`, even if `Dump` returns an error. This is most likely to happen when
evaluating an object description, ie `po`.
This changes dwim-print to continue on to expression evaluation when `Dump`ing a
variable returns an error . This is to allow for diagnostics that match `expression`.