Add HTTP2 client support (without TLS)

[pulkit4tech]

• Description and context for reviewers: one partner, one stranger
  • Added Config support to useHTTP2 in outbounds
  • Updated Outbound to support HTTP2 client based on config
• Entry in CHANGELOG.md

[codecov]

Codecov Report

Attention: Patch coverage is 79.31034% with 6 lines in your changes missing coverage. Please review.

Project coverage is 85.22%. Comparing base (0b37e42) to head (152f52f).
Report is 1 commits behind head on dev.

Files with missing lines	Patch %	Lines
transport/http/outbound.go	77.77%	4 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #2330      +/-   ##
==========================================
- Coverage   85.24%   85.22%   -0.03%     
==========================================
  Files         271      271              
  Lines       15619    15642      +23     
==========================================
+ Hits        13315    13331      +16     
- Misses       1881     1884       +3     
- Partials      423      427       +4     

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