Support mongo driver 4.x version.

[harvies]

Please answer these questions before submitting a pull request

• Why submit this pull request?

• Bug fix

• New feature provided

• Improve performance

• Related issues

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Bug fix

• Bug description.

• How to fix?

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New feature or improvement

• Describe the details and related test reports.

[codecov]

Codecov Report

Merging #5512 into master will decrease coverage by 0.15%.
The diff coverage is 26.85%.

@@             Coverage Diff              @@
##             master    #5512      +/-   ##
============================================
- Coverage     52.54%   52.39%   -0.16%     
- Complexity     3361     3364       +3     
============================================
  Files          1596     1603       +7     
  Lines         33947    34097     +150     
  Branches       3695     3720      +25     
============================================
+ Hits          17839    17866      +27     
- Misses        15256    15370     +114     
- Partials        852      861       +9     

Impacted Files	Coverage Δ	Complexity Δ
...ugin/mongodb/v4/support/MongoRemotePeerHelper.java	0.00% <0.00%> (ø)	0.00 <0.00> (?)
...lugin/mongodb/v4/support/MongoOperationHelper.java	7.46% <7.46%> (ø)	0.00 <0.00> (?)
.../interceptor/MongoDBClientDelegateInterceptor.java	42.85% <42.85%> (ø)	0.00 <0.00> (?)
...terceptor/MongoDBOperationExecutorInterceptor.java	83.33% <83.33%> (ø)	0.00 <0.00> (?)
...apm/plugin/mongodb/v4/support/MongoSpanHelper.java	85.71% <85.71%> (ø)	0.00 <0.00> (?)
...m/plugin/mongodb/v4/support/MongoPluginConfig.java	100.00% <100.00%> (ø)	0.00 <0.00> (?)
...alking/apm/agent/core/context/util/PeerFormat.java	25.00% <0.00%> (-8.34%)	0.00% <0.00%> (ø%)
...erver/library/server/grpc/CustomThreadFactory.java	69.23% <0.00%> (-7.70%)	2.00% <0.00%> (-1.00%)
...core/analysis/manual/instance/InstanceTraffic.java	54.00% <0.00%> (-6.00%)	6.00% <0.00%> (-1.00%)
...er/storage/plugin/influxdb/query/MetricsQuery.java	43.92% <0.00%> (-0.94%)	8.00% <0.00%> (-1.00%)
... and 13 more

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[wu-sheng]

Basically, good to me. Several doc nits. And Test should be enhanced a little.

[harvies]

Can you retry the failed CI check for me?