Append user agent for retry mode

[Quanzzzz]

Append user agent for retry mode so we can collect the metrics of the usage of each retry mode.

Testing

A unit test is added

[codecov-io]

Codecov Report

Merging #2322 (270b395) into master (b9bc77d) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master    #2322      +/-   ##
============================================
+ Coverage     77.64%   77.67%   +0.02%     
  Complexity      366      366              
============================================
  Files          1239     1239              
  Lines         39033    39041       +8     
  Branches       3081     3081              
============================================
+ Hits          30307    30324      +17     
+ Misses         7256     7249       -7     
+ Partials       1470     1468       -2     

Flag	Coverage Δ	Complexity Δ
unittests	77.67% <100.00%> (+0.02%)	0.00 <0.00> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ	Complexity Δ
...rnal/http/pipeline/stages/ApplyUserAgentStage.java	95.83% <100.00%> (+0.71%)	0.00 <0.00> (ø)
...software/amazon/awssdk/core/retry/RetryPolicy.java	59.61% <100.00%> (+1.36%)	0.00 <0.00> (ø)
...ssdk/core/internal/async/FileAsyncRequestBody.java	83.01% <0.00%> (+1.88%)	0.00% <0.00%> (ø%)
...mazon/awssdk/utils/internal/MappingSubscriber.java	89.65% <0.00%> (+6.89%)	0.00% <0.00%> (ø%)
...k/core/pagination/async/ResponsesSubscription.java	88.00% <0.00%> (+16.00%)	0.00% <0.00%> (ø%)

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[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!

0 Bugs
0 Vulnerabilities
0 Security Hotspots
2 Code Smells

100.0% Coverage
0.0% Duplication