[lldb] UpdateFormatsIfNeeded should respect the dynamic value type (#93262)

UpdateFormatsIfNeeded has hardcoded the call to GetFormat with no
dynamic values. GetFormat will try to find the synthetic children of the
ValueObject, and passing the wrong one can fail, which can be bad for
performance but should not be user visible. Fix the performace bug by
passing the dynamic value type of the ValueObject.

rdar://122506593