Add stubs for new activity execution APIs #26066

Job	Run time
Test setup	14s
Pre-build for cache	1m 35s
Misc checks	4m 11s
Integration test	4m 9s
Unit test	6m 7s
Mixed brain test	7m 58s
Functional test (cass_es, shard2)	17m 17s
Functional test (cass_es, shard1)	15m 16s
Functional test (sqlite, smoke)	2m 38s
Functional test (cass_es, shard0)	18m 3s
Functional test (cass_os3, smoke)	3m 53s
Functional test (cass_es, ndc)	3m 35s
Functional test (mysql8, smoke)	3m 9s
Functional test (cass_es, xdc)	10m 18s
Functional test (cass_es8, smoke)	3m 39s
Functional test (postgres12, shard0)	16m 43s
Functional test (postgres12, shard1)	14m 46s
Functional test (postgres12, ndc)	2m 54s
Functional test (cass_os2, smoke)	3m 43s
Functional test (postgres12_pgx, smoke)	2m 59s
Functional test (postgres12, xdc)	9m 10s
Functional test (postgres12, shard2)	11m 3s
Test Status	3s
Notify Slack on Failure	0s
	2h 43m 23s

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