[#7742] export trace info for agent-sdk

[yjqg6666]

Resolve issue #7742.
Related PR #6801.

Feature

Export txId & spanId to application via pinpoint agent sdk. Disabled by default. It can be enabled by pinpoint config profiler.export.trace.info=true or jvm property: -Dprofiler.export.trace.info=true.

Usage

If my application need to save/notify some system the txId/spanId, i could

1. import com.navercorp.pinpoint:pinpoint-agent-sdk:2.5.0-SNAPSHOT as dependency.

<dependency>
   <groupId>com.navercorp.pinpoint</groupId>
   <artifactId>pinpoint-agent-sdk</artifactId>
   <version>2.5.0-SNAPSHOT</version>
</dependency>

2. fetch the txId/spanId

TraceInfo traceInfo = TraceInfoHolder.getTraceInfo();
String altTxId = traceInfo.getTransactionId();
String txId = TraceInfoHolder.getTransactionId();
long spanId = TraceInfoHolder.getSpanId();

Scene

Get the transaction id and process it in a programming way(like saving to a persistent db).

Before this PR, we could only get the txId/spanId from slf4j.MDC in a hacky way.

[yjqg6666]

Got unrelated test failure: https://github.com/pinpoint-apm/pinpoint/runs/8281315683?check_suite_focus=true#step:8:14881.

[codecov]

Codecov Report

Merging #9175 (e7b1184) into master (d745085) will decrease coverage by 0.03%.
The diff coverage is 0.00%.

@@             Coverage Diff              @@
##             master    #9175      +/-   ##
============================================
- Coverage     39.84%   39.80%   -0.04%     
- Complexity    11748    11749       +1     
============================================
  Files          3361     3364       +3     
  Lines         90639    90705      +66     
  Branches      10085    10094       +9     
============================================
- Hits          36113    36107       -6     
- Misses        51445    51518      +73     
+ Partials       3081     3080       -1     

Impacted Files	Coverage Δ
...otstrap/plugin/request/ServletRequestListener.java	0.00% <0.00%> (ø)
...ootstrap/plugin/request/util/ClassLoaderUtils.java	0.00% <0.00%> (ø)
...rap/plugin/request/util/TraceInfoExportHelper.java	0.00% <0.00%> (ø)
...p/pinpoint/rpc/stream/StreamChannelRepository.java	57.89% <0.00%> (-21.06%)	⬇️
...vercorp/pinpoint/rpc/packet/ClientClosePacket.java	46.66% <0.00%> (-6.67%)	⬇️
...rc/main/java/com/navercorp/pinpoint/test/Item.java	68.51% <0.00%> (-3.71%)	⬇️
...ollector/cluster/zookeeper/ZookeeperJobWorker.java	78.49% <0.00%> (-1.62%)	⬇️
...point/rpc/client/DefaultPinpointClientHandler.java	70.42% <0.00%> (-1.41%)	⬇️
...orp/pinpoint/rpc/server/DefaultPinpointServer.java	79.83% <0.00%> (-1.24%)	⬇️
...npoint/metric/web/mybatis/DataSourceDelegator.java	21.42% <0.00%> (ø)
... and 7 more

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