Resolve "Rewrite AlleleFilter.filter_alleles/filter_analysis to take in filter config object rather than id"

Description

In addition to the change highlighted in the issue, the following was done:

• Removed AlleleFilter.filter_alleles as this was unused leftover from when we did filtering on the overview page.
• Added FilterBase base-class for all filters, to distinguish between filters needing only alleles, genepanel + alleles, or analysis + alleles, and to separate filters where the context of an allele is important.
• All filters now have a filter function (either filter_with_alleles, filter_with_genepanel, or filter_with_analysis) which only works on a single analysis/genepanel/set of alleles. The ability to work on multiple analyses (or genepanels) simultaneously was also an unused leftover feature from when we did filtering on the overview page.
• Minor typing cleanup.

Notes to review (code/docs/QA)

None of the actual filter functionality has changed. Most of the changes are basic indentation changes due to the fact that we no longer loop over analysis_ids or gp_keys inside the function.

No tests have been removed or fundamentally changed.

Possibly useful to go through changes up to a3210dae, and after this separately.

Related issues

Closes #2230 (closed)