Add ClientFactory.numConnections()

[kojilin]

Motivation:

It's be nice if ClientFactory has numConnections() like Server,
so that a user can easily figure out how many connections it is managing.

Modifications:

• Add Clientfactory.numConnections(), get connection count from allChannels directly.
• Add test for multiple h1c request & multie servers

Result:

• Closes Add ClientFactory.numConnections() #3596

[trustin]

Thank you so much for working on this, @kojilin 🙇

[codecov]

Codecov Report

Merging #3613 (d01e669) into master (1b6c3b7) will increase coverage by 0.04%.
The diff coverage is 75.00%.

❗ Current head d01e669 differs from pull request most recent head 0fa2bec. Consider uploading reports for the commit 0fa2bec to get more accurate results

@@             Coverage Diff              @@
##             master    #3613      +/-   ##
============================================
+ Coverage     73.81%   73.85%   +0.04%     
- Complexity    14356    14381      +25     
============================================
  Files          1260     1263       +3     
  Lines         54820    54878      +58     
  Branches       7022     7021       -1     
============================================
+ Hits          40463    40528      +65     
+ Misses        10785    10779       -6     
+ Partials       3572     3571       -1     

Impacted Files	Coverage Δ
...ava/com/linecorp/armeria/client/ClientFactory.java	65.33% <ø> (ø)
...necorp/armeria/client/DecoratingClientFactory.java	37.03% <0.00%> (-1.43%)	⬇️
.../linecorp/armeria/client/DefaultClientFactory.java	72.34% <100.00%> (+2.44%)	⬆️
...a/com/linecorp/armeria/client/HttpChannelPool.java	78.74% <100.00%> (+0.33%)	⬆️
...com/linecorp/armeria/client/HttpClientFactory.java	85.71% <100.00%> (+0.11%)	⬆️
...p/armeria/common/stream/AbstractStreamMessage.java	79.80% <0.00%> (-1.93%)	⬇️
...uth/oauth2/OAuth2TokenIntrospectionAuthorizer.java	63.15% <0.00%> (-1.76%)	⬇️
...inecorp/armeria/server/HttpResponseSubscriber.java	77.89% <0.00%> (-1.06%)	⬇️
...ia/internal/common/stream/ByteBufDecoderInput.java	84.89% <0.00%> (-0.72%)	⬇️
.../linecorp/armeria/client/Http1ResponseDecoder.java	66.66% <0.00%> (-0.61%)	⬇️
... and 26 more

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[ikhoon]

Thanks a lot! @kojilin

[minwoox]

👍 👍 👍