feat: Make SESSION_COOKIE_AGE explicit #33215

Job	Run time
collect-and-verify	2m 55s
lms-1(py=3.11,dj=pinned,mongo=7.0)	9m 11s
lms-2(py=3.11,dj=pinned,mongo=7.0)	10m 40s
lms-3(py=3.11,dj=pinned,mongo=7.0)	13m 52s
lms-4(py=3.11,dj=pinned,mongo=7.0)	18m 48s
lms-5(py=3.11,dj=pinned,mongo=7.0)	11m 6s
lms-6(py=3.11,dj=pinned,mongo=7.0)	14m 45s
openedx-1-with-lms(py=3.11,dj=pinned,mongo=7.0)	9m 53s
openedx-2-with-lms(py=3.11,dj=pinned,mongo=7.0)	12m 58s
openedx-1-with-cms(py=3.11,dj=pinned,mongo=7.0)	7m 7s
openedx-2-with-cms(py=3.11,dj=pinned,mongo=7.0)	5m 19s
cms-1(py=3.11,dj=pinned,mongo=7.0)	3m 15s
cms-2(py=3.11,dj=pinned,mongo=7.0)	11m 35s
common-with-lms(py=3.11,dj=pinned,mongo=7.0)	8m 14s
common-with-cms(py=3.11,dj=pinned,mongo=7.0)	3m 53s
xmodule-with-lms(py=3.11,dj=pinned,mongo=7.0)	7m 35s
xmodule-with-cms(py=3.11,dj=pinned,mongo=7.0)	7m 13s
xmodule-with-cms(py=3.11,dj=pinned,mongo=7.0)	7m 21s
xmodule-with-lms(py=3.11,dj=pinned,mongo=7.0)	7m 48s
Unit tests successful	1s
compile-warnings-report	8s
coverage (3.11)	1m 31s
merge-artifacts	11s
	2h 55m 19s

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