Simplify the do_filtered_draw hook

[Zalathar]

This is a small piece of cleanup that I've been meaning to do for a while.

Originally, the do_filtered_draw hook was added as a lightweight way for individual strategies to make filtering more efficient (specifically sampled_from in #1904), without having to fully override .filter with a custom strategy.

(At the time, no non-trivial strategy had a custom .filter implementation, so this was worthwhile.)

Over time, a few things changed:

• The hook was also used by UniqueListStrategy (Efficient unique collections with elements from a sampled_from  #1891)
• Unique lists of sampled_from were further specialized to UniqueSampledListStrategy (Improve performance of unique lists with elements=sampled_from(...) #2031), bypassing the generic code in UniqueListStrategy
• More non-trivial implementations of .filter were added to rewrite simple filters on integers() into bounds updates (Rewrite simple filters for bounded integers() #2853)

All together, these developments mean that the original design of do_filtered_draw is now more of a liability, adding confusion for little gain.

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This PR therefore greatly simplifies the design of do_filtered_draw by omitting the filter_strategy argument, and changing its contract to simply be “like do_draw, but if filtering fails then return a sentinel instead of throwing”.

Furthermore, most strategies now no longer have a do_filtered_draw method at all. Instead they have a _filter_for_filtered_draw method, which returns an object (currently always FilteredStrategy) that implements do_filtered_draw.

(Note that SampledFromStrategy still has a do_filtered_draw method, but currently it never actually gets called by UniqueListStrategy because of the UniqueFilteredListStrategy specialization. I've left it as-is for now, partly because it would work if needed, and partly to avoid having to merge that code back into SampledFromStrategy.do_draw for no real benefit.)

[Zac-HD]

This looks great - thanks Zalathar. I really appreciate all the cleanup work you've been doing lately 😍