http: server error handling improvements and tests

[gdamore]

We want to consume the request properly on an error, so that we can give a reasonable response. We were prematurely closing the connection for certain failure modes. We still have to fix overly long URIs and headers, but thats next!

fixes #

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[codecov]

Codecov Report

Attention: Patch coverage is 65.00000% with 7 lines in your changes missing coverage. Please review.

Project coverage is 83.66%. Comparing base (169166a) to head (c34abc2).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/supplemental/http/http_msg.c	53.33%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2083      +/-   ##
==========================================
+ Coverage   83.57%   83.66%   +0.08%     
==========================================
  Files          93       93              
  Lines       23501    23503       +2     
  Branches     3035     3035              
==========================================
+ Hits        19642    19663      +21     
+ Misses       3783     3762      -21     
- Partials       76       78       +2     

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