Remove support for python 3.8 #3808

Job	Run time
lint-crlf	4s
check-lockfile	5s
changes	3s
lint-newsfile	36s
Typechecking	1m 31s
check-schema-delta	40s
lint	21s
check-sampleconfig	40s
lint-clippy	18s
lint-clippy-nightly	17s
lint-pydantic	39s
lint-readme	0s
lint-rustfmt	19s
linting-done	3s
calculate-test-jobs	5s
trial-olddeps	7m 13s
portdb (3.9, 11)	3m 1s
complement (monolith, SQLite)	14m 11s
trial-pypy	0s
portdb (3.11, 15)	3m 1s
complement (monolith, Postgres)	14m 39s
complement (workers, Postgres)	22m 2s
cargo-bench	0s
cargo-test	0s
trial (3.9, sqlite, all)	6m 5s
sytest (bullseye)	8m 24s
trial (3.9, postgres, 11, all)	13m 41s
sytest (bullseye, postgres)	10m 16s
trial (3.9, sqlite)	5m 29s
sytest (bullseye, multi-postgres, workers)	14m 19s
sytest (bullseye, multi-postgres, workers, asyncio)	19m 11s
export-data	2m 9s
tests-done	4s
	2h 29m 26s

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