Configurable HTTP Address

[Cleptomania]

Issue #, if available:
#68

Description of changes:
A first run implementation of a configurable HTTP listen address

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 73.58491% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 42.22%. Comparing base (febfa7d) to head (00013f2).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
aws_secretsmanager_agent/src/config.rs	69.56%	14 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #69      +/-   ##
==========================================
+ Coverage   41.92%   42.22%   +0.29%     
==========================================
  Files          14       14              
  Lines        8524     8548      +24     
==========================================
+ Hits         3574     3609      +35     
+ Misses       4950     4939      -11     

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