Documentation: Add release calendars for 2025 and 2026. #4776

Job	Run time
osx clang --disable-ssl	1m 56s
linux rpm fedora	7m 12s
Prepare container	3m 15s
linux gcc --disable-ssl	2m 50s
linux clang --disable-ssl	2m 49s
linux gcc test -300	9m 23s
linux gcc test 301-600	6m 20s
linux gcc test 601- unstable	6m 46s
linux clang test sanitizers -300	12m 40s
linux clang test sanitizers 301-600	9m 18s
linux clang test sanitizers 601- unstable	11m 39s
linux gcc test -ljemalloc -300	9m 39s
linux gcc test -ljemalloc 301-600	6m 47s
linux gcc test -ljemalloc 601- unstable	6m 59s
linux gcc system-test-dpdk dpdk -100	16m 45s
linux gcc system-test-dpdk dpdk 101- unstable	14m 56s
linux gcc system-test-userspace -100	15m 46s
linux gcc system-test-userspace 101- unstable	13m 46s
linux gcc system-test -100	18m 19s
linux gcc system-test 101- unstable	18m 11s
linux clang system-test sanitizers -100	20m 13s
linux clang system-test sanitizers 101- unstable	20m 7s
linux x86 gcc --disable-ssl	2m 48s
	3h 58m 24s

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