Merge 11.4 into 11.8 - null-merge MDEV-39240

A jira to cover PR#4976:

Merge branch 11.4 into 11.8 as part of the Q2 2026 release.

MDEV-39240 is null-merged (excluded) as if removed by MDEV-32188.

MDEV-39240 fixed a replication issue where pre-11.5 replicas accepted
timestamps beyond Year 2038 via row-based replication, introduced as a
side effect of MDEV-32188 being a preview feature in 11.4. In 11.8,
MDEV-32188 is fully released and the extended timestamp range is stable,
so MDEV-39240 does not apply and must not be merged.

This was requested by Jimmy Hú in the Q2 2026 release task (MDEV-39403).