Replace RestTemplate with OkHttp for system tests #3324

Job	Run time
system-test (sentry-samples-spring-boot-jakarta, 0, true)	6m 38s
system-test (sentry-samples-spring-boot-jakarta, 0, true)	6m 38s
system-test (sentry-samples-spring-boot)	6m 20s
system-test (sentry-samples-spring-boot)	6m 20s
system-test (sentry-samples-spring-boot-opentelemetry-noagent)	6m 20s
system-test (sentry-samples-spring-boot-opentelemetry-noagent)	6m 20s
system-test (sentry-samples-spring-boot-opentelemetry, 1, true)	6m 53s
system-test (sentry-samples-spring-boot-opentelemetry, 1, true)	6m 39s
system-test (sentry-samples-spring-boot-opentelemetry, 1, false)	6m 40s
system-test (sentry-samples-spring-boot-opentelemetry, 1, false)	6m 40s
system-test (sentry-samples-spring-boot-webflux-jakarta)	5m 20s
system-test (sentry-samples-spring-boot-webflux-jakarta)	5m 20s
system-test (sentry-samples-spring-boot-webflux)	5m 12s
system-test (sentry-samples-spring-boot-webflux)	5m 12s
system-test (sentry-samples-spring-boot-jakarta-opentelemetry-noagent)	6m 31s
system-test (sentry-samples-spring-boot-jakarta-opentelemetry-noagent)	6m 31s
system-test (sentry-samples-spring-boot-jakarta-opentelemetry, 1, true)	6m 28s
system-test (sentry-samples-spring-boot-jakarta-opentelemetry, 1, true)	6m 28s
system-test (sentry-samples-spring-boot-jakarta-opentelemetry, 1, false)	7m 4s
system-test (sentry-samples-spring-boot-jakarta-opentelemetry, 1, false)	7m 4s
	2h 6m 38s

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