Make metrics ip and port, and http endpoint port configurable

[mickel8]

This PR allows for running multiple JF instances in development. In particular:

• allow for configuring prometheus metrics port and ip
• allow for configuring http endpoint port in development
• change ConfigParser to ConfigReader and move it to a separate file - runtime.exs is read after compilation so we can keep ConfigReader in lib directory making runtime.exs clearer
• limit prod mandatory fields by generating SECRET_KEY_BASE when it's not passed and allowing for passing CHECK_ORIGIN not only in prod - this way we have only two prod mandatory variables i.e. VIRTUAL_HOST and SERVER_API_TOKEN.

[codecov[bot]]

Codecov Report

Merging #87 (cd00d5b) into main (bbff33a) will increase coverage by 0.56%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #87      +/-   ##
==========================================
+ Coverage   83.70%   84.27%   +0.56%     
==========================================
  Files          43       44       +1     
  Lines         718      744      +26     
==========================================
+ Hits          601      627      +26     
  Misses        117      117              

Files Changed	Coverage Δ
lib/jellyfish/config_reader.ex	100.00% <100.00%> (ø)
lib/jellyfish_web/telemetry.ex	100.00% <100.00%> (ø)

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