Add freethreading Python 3.14 and 3.15 #289

Job	Run time
Build, test and push (amd64, py36,py39,py310,py311,py312,py313,py314,py315,py314t,py315t,pypy,pyp...	4m 22s
Build, test and push (arm64, py312)	23m 22s
Build, test and push (ppc64le, py39,py311)	19m 53s
Build, test and push (s390x, py39,py310,py312)	22m 16s
Update Dockerhub description	5s
Update and test manifests	3m 7s
	1h 13m 5s

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