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

**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 https://github.com/HDFGroup/hdf5/pull/5025 with a new `--lformat` command-line option to specify the printing format for `long double` data. In https://github.com/HDFGroup/hdf5/pull/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)`.