This change adds support for using `search_after` with field collapsing. When
using these in conjunction, the same field must be used for both sorting and
field collapsing. This helps keep the behavior simple and predictable.
Otherwise it would be possible for a group to appear on multiple pages of
results.
Currently search after is handled directly in `CollapsingTopDocsCollector`. As
a follow-up, we could generalize the logic and move support to the Lucene
grouping framework.
Closes#53115.
f85a9dddb9