Update h5dump's --lformat option to set the format for long double _Complex numbers

[jhendersonHDF]

Is your feature request related to a problem? Please describe.
h5dump currently has no method for specifying the printing format for long double _Complex data, unless the size of long double _Complex matches the size of double _Complex (mostly on Windows).

Describe the solution you'd like
h5dump was recently updated in #5025 with a new --lformat command-line option to specify the printing format for long double data. In #4630, h5dump was updated so that its --format option specifies the printing format for float _Complex and double _Complex data, as well as long double _Complex if it's the same size as double _Complex. h5dump's new --lformat should be updated to cover setting the printing format for long double _Complex data in the case where sizeof(long double _Complex) != sizeof(double _Complex).