p2p: reuse existing libp2p.Host for http clients

[algorandskiy]

Summary

In some scenarios GetPeers for archival role gets called too often, and each time new libp2p.Host gets created that causes high memory usage.

Although this fix is good as is, the underlying issue with high GetPeers invocation rate is under investigation.

Test Plan

Tested manually against devnet.

[codecov]

Codecov Report

Attention: Patch coverage is 7.69231% with 24 lines in your changes missing coverage. Please review.

Project coverage is 56.17%. Comparing base (3b3b5ce) to head (35c3ec5).
Report is 3 commits behind head on master.

Files with missing lines	Patch %	Lines
network/p2p/http.go	0.00%	21 Missing ⚠️
network/p2p/p2p.go	0.00%	2 Missing ⚠️
network/p2pNetwork.go	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6129      +/-   ##
==========================================
+ Coverage   54.28%   56.17%   +1.88%     
==========================================
  Files         494      494              
  Lines       69936    69951      +15     
==========================================
+ Hits        37968    39297    +1329     
+ Misses      29246    27981    -1265     
+ Partials     2722     2673      -49     

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