CLSA-2026-1779465893 postgresql: Fix of CVE-2026-6473

CVE-2026-6473: tsearch: bound StartSel/StopSel/FragmentDelimiter length to PGINT16MAX in tsheadline - CVE-2026-6473: contrib/ltree: guard lquery parsing against numvar and totallen wraparound - CVE-2026-6473: regex: add overflow-checked MALLOCARRAY/REALLOCARRAY and bound NFA state/color products...