### Description

From the nodes stats API, we should extract the `thread_pool` stats into their own endpoint. This endpoint can then be non-node-centric, and present a global view of the number of completed, rejected, and failed operations for each of the threadpools in the system.
server/src/test/java/org/elasticsearch/action/admin/cluster/node/stats/NodeStatsTests.java
}
            JvmStats.GarbageCollectors garbageCollectors = new JvmStats.GarbageCollectors(garbageCollectorsArray);
            int numBufferPools = randomIntBetween(0, 10);
            List<JvmStats.BufferPool> bufferPoolList = new ArrayList<>();
            for (int i = 0; i < numBufferPools; i++) {
                bufferPoolList.add(
                    new JvmStats.BufferPool(
                        randomAlphaOfLengthBetween(3, 10),
                        randomNonNegativeLong(),
                        randomNonNegativeLong(),
                        randomNonNegativeLong()
                    )
                );
            }
            JvmStats.Classes classes = new JvmStats.Classes(randomNonNegativeLong(), randomNonNegativeLong(), randomNonNegativeLong());
            jvmStats = frequently()
                ? new JvmStats(
                    randomNonNegativeLong(),
                    randomNonNegativeLong(),
                    new JvmStats.Mem(
                        randomNonNegativeLong(),
                        randomNonNegativeLong(),
                        randomNonNegativeLong(),
                        randomNonNegativeLong(),
                        randomNonNegativeLong(),
                        memoryPools
                    ),
                    threads,
                    garbageCollectors,
                    randomBoolean() ? Collections.emptyList() : bufferPoolList,