[22841] Improve `max_allocations` calculation on SHM transport #1778

Job	Run time
sanitizers-ci / asan_fastdds_build	6m 28s
sanitizers-ci / tsan_fastdds_test	17m 0s
sanitizers-ci / asan_discovery_server_test	5m 48s
sanitizers-ci / asan_fastdds_test	10m 22s
	39m 38s

Provide feedback