range raptor early termination

[mority]

for range queries:
stop searching the interval in case of a non-zero min. connection count being already reached and

• search dir == fwd && extend allowed only earlier
• search dir == bwd && extend allowed only later

all algorithms used by search.h should support this, PONG is not affected since it implements its own search approach

[mority]

Frankfurt Konstablerwache -> Frankfurt Hbf, initial PONG and subsequent click on "earlier"

min #itineraries: 5, extend_ealier: false, extend_later: true, search_interval: [2026-02-24 14:00, 2026-02-24 14:15[
search_interval.size: 15min
search interval reduction by early termination: 0min
events skipped by early termination: 0
min #itineraries: 5, extend_ealier: true, extend_later: false, search_interval: [2026-02-24 13:50, 2026-02-24 14:00[
search_interval.size: 10min
search interval reduction by early termination: 470min
events skipped by early termination: 5537

PONG & rraptor with early termination, a perfect match 🥲

[mority]

FWD and later uses PONG, FWD and earlier can use rRAPTOR with early termination therefore I would argue that this PR closes #258. We do not need to estimate interval sizes anymore since we always stop once we fulfilled the min. connection count.