Rename subproject `java21` to `java21-test` (#3251) #1894

Job	Run time
android (26)	5m 55s
build (11, mock-maker-default, member-accessor-default)	7m 40s
android (33)	5m 42s
build (11, mock-maker-inline, member-accessor-module)	8m 18s
build (11, mock-maker-subclass, member-accessor-module)	7m 37s
build (11, mock-maker-subclass, member-accessor-reflection)	7m 23s
build (11, mock-maker-inline, member-accessor-reflection)	8m 2s
build (17, mock-maker-default, member-accessor-default)	6m 1s
build (17, mock-maker-inline, member-accessor-module)	7m 41s
build (17, mock-maker-subclass, member-accessor-module)	6m 42s
build (17, mock-maker-subclass, member-accessor-reflection)	7m 21s
build (17, mock-maker-inline, member-accessor-reflection)	7m 30s
build (21, mock-maker-default, member-accessor-default)	5m 56s
build (21, mock-maker-inline, member-accessor-module)	7m 35s
build (21, mock-maker-subclass, member-accessor-module)	6m 40s
build (21, mock-maker-subclass, member-accessor-reflection)	6m 46s
build (21, mock-maker-inline, member-accessor-reflection)	7m 29s
release	2m 6s
	2h 2m 24s

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