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- [ ] I have searched the [issues](https://github.com/apache/dubbo/issues) of this repository and believe that this is not a duplicate.

## Describe the proposal
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EN:
Observability task, optimizing thread pool index embedding function
1 Need to specify a name for the core thread pool
2 Core thread pool index is not effective
3. Remove the frame-level indicators and only keep the core monitoring indicators (the frame-level code type is completely deleted and will be considered later)

可观测性任务，优化线程池指标埋点功能
1需要为核心线程池指定名称
2核心线程池指标生效问题
3移除框架层指标只保留核心监控指标
import org.apache.dubbo.metrics.collector.sample.SimpleMetricsCountSampler;
import org.apache.dubbo.metrics.collector.sample.ThreadPoolMetricsSampler;
import org.apache.dubbo.metrics.event.MetricsEvent;
import org.apache.dubbo.metrics.event.SimpleMetricsEventMulticaster;
import org.apache.dubbo.metrics.listener.MetricsListener;
import org.apache.dubbo.metrics.model.ApplicationMetric;
import org.apache.dubbo.metrics.model.sample.GaugeMetricSample;
import org.apache.dubbo.metrics.model.sample.MetricSample;
import org.apache.dubbo.rpc.model.ApplicationModel;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.atomic.AtomicLong;
import static org.apache.dubbo.metrics.model.MetricsCategory.APPLICATION;
import static org.apache.dubbo.metrics.model.MetricsKey.APPLICATION_METRIC_INFO;
/**
 * Default implementation of {@link MetricsCollector}
 */
public class DefaultMetricsCollector implements MetricsCollector {
    private boolean collectEnabled = false;
    private final SimpleMetricsEventMulticaster eventMulticaster;
    private final MethodMetricsSampler methodSampler = new MethodMetricsSampler(this);
    private final ThreadPoolMetricsSampler threadPoolSampler = new ThreadPoolMetricsSampler(this);
    private String applicationName;
    private ApplicationModel applicationModel;
    private final List<MetricsSampler> samplers = new ArrayList<>();
    public DefaultMetricsCollector() {
        this.eventMulticaster = new SimpleMetricsEventMulticaster();
        samplers.add(methodSampler);
        samplers.add(applicationSampler);
        samplers.add(threadPoolSampler);