Update docker images to Alpine 3.21 #1592

Job	Run time
static-analysis (8.3, cs)	1m 3s
static-analysis (8.3, stan)	50s
static-analysis (8.3, openapi:validate)	22s
api-tests / tests (8.3)	5m 4s
cli-tests / tests (8.3)	57s
api-tests / tests (8.4)	3m 47s
cli-tests / tests (8.4)	52s
unit-tests / tests (8.3)	46s
unit-tests / tests (8.4)	1m 3s
db-tests (mysql) / db-tests (8.3)	49s
db-tests (maria) / db-tests (8.3)	44s
db-tests (mysql) / db-tests (8.4)	42s
db-tests (maria) / db-tests (8.4)	46s
db-tests (ms) / db-tests (8.3)	54s
db-tests (ms) / db-tests (8.4)	4m 27s
db-tests (postgres) / db-tests (8.3)	2m 34s
db-tests (sqlite:ci) / db-tests (8.3)	43s
db-tests (postgres) / db-tests (8.4)	3m 5s
db-tests (sqlite:ci) / db-tests (8.4)	40s
upload-coverage (8.3)	2m 11s
delete-artifacts	1s
	32m 20s

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