Refactor `filter` and `laterality` modules: `joblib` is not optional

[jhlegarreta]

The filter and laterality modules try to use joblib modules conditionally if importing it is successful: https://github.com/SlicerDMRI/whitematteranalysis/blob/ac6040fcf77ac132d0fc4a071af9d80240f7f577/whitematteranalysis/filter.py#L32 https://github.com/SlicerDMRI/whitematteranalysis/blob/ac6040fcf77ac132d0fc4a071af9d80240f7f577/whitematteranalysis/laterality.py#L35

However, joblib is a required dependency:, https://github.com/SlicerDMRI/whitematteranalysis/blob/ac6040fcf77ac132d0fc4a071af9d80240f7f577/requirements.txt#L1

so the if/else blocks in the above modules are not necessary, e.g. (there are multiple hits): https://github.com/SlicerDMRI/whitematteranalysis/blob/ac6040fcf77ac132d0fc4a071af9d80240f7f577/whitematteranalysis/filter.py#L610 https://github.com/SlicerDMRI/whitematteranalysis/blob/ac6040fcf77ac132d0fc4a071af9d80240f7f577/whitematteranalysis/laterality.py#L167

Removing the conditional blocks may require some work, as the else blocks seem to contain a more complex/different logic with respect to the counterpart using the parallelization capabilities.