Create message-kind-specific parse methods and remove circular dependency

[diehuxx]

• Create specific message parsers e.g. Rfq.parse() which will ensure the payload is an RFQ message and can be easily extended to do RFQ-specific validation
• Move Message.parse() into Parser.parseMessage() because Message.parse() caused Message to depend on its subclasses, which is a violation of OOP best practices and constitutes a circular dependency.

[codecov-commenter]

Codecov Report

Merging #224 (16aabda) into main (bd505a5) will increase coverage by 0.72%.
Report is 3 commits behind head on main.
The diff coverage is 92.04%.

❗ Current head 16aabda differs from pull request most recent head dae6bb2. Consider uploading reports for the commit dae6bb2 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #224      +/-   ##
==========================================
+ Coverage   79.39%   80.11%   +0.72%     
==========================================
  Files          35       36       +1     
  Lines         820      875      +55     
  Branches       75       82       +7     
==========================================
+ Hits          651      701      +50     
- Misses        133      136       +3     
- Partials       36       38       +2     

Components	Coverage Δ
protocol	88.47% <91.66%> (+0.45%)	⬆️
httpclient	80.82% <100.00%> (ø)