[BUG] Convert LALDict to python dictionary before saving

[adivijaykumar]

Fixes #751. Uses lalsimulation.gwsignal.core.utils.from_lal_dict to convert a LALDict to a python dictionary before saving.
I have a few concerns which I was not sure how to tackle:

The new logic has the downside that it is the only part of code in core/result.py that depends on a function in gw. The other option is to define an equivalent _get_save_data_dictionary inside the CompactBinaryCoalescenceResult class.
Right now this imports the relevant function from LALSimulation, but we could have just copied over the relevant code into bilby (since LALSuite is under GNU GPL).

Migrated from git.ligo: https://git.ligo.org/lscsoft/bilby/-/merge_requests/1309

[adivijaykumar]

Comment from Colm on the original MR:

I think it would be neater to have this in this class https://git.ligo.org/lscsoft/bilby/-/blob/master/bilby/core/utils/io.py#L29 and a coresponding deserialiser in https://git.ligo.org/lscsoft/bilby/-/blob/master/bilby/core/utils/io.py#L148.
We may also need a pair for hdf5 (https://git.ligo.org/lscsoft/bilby/-/blob/master/bilby/core/utils/io.py#L209, https://git.ligo.org/lscsoft/bilby/-/blob/master/bilby/core/utils/io.py#L247). The main issue is that we should not add an import of lalsimulation at the top of that method. For the encoder I'd suggest something like we do for e.g., pandas objects