[8.19] Adding merging logic to recursive chunking and renaming SeparatorSet to SeparatorGroup (#131103)#131227

dan-rubinstein merged 3 commits intoelastic:8.19elastic/elasticsearch:8.19from

dan-rubinstein:backport/8.19/pr-131103dan-rubinstein/elasticsearch:backport/8.19/pr-131103Copy head branch name to clipboard