Support custom data dictionaries

[davidsteiner]

This change makes the data_dictionary_path config value actually work, rather than always relying on the standard FIX 4.4 data dictionary.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 10 lines in your changes missing coverage. Please review.

Project coverage is 43.45%. Comparing base (21f48c4) to head (a5396c5).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/hotfix/src/session.rs	0.00%	7 Missing ⚠️
crates/hotfix-dictionary/src/lib.rs	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #101      +/-   ##
==========================================
- Coverage   43.62%   43.45%   -0.17%     
==========================================
  Files          57       57              
  Lines        2414     2423       +9     
==========================================
  Hits         1053     1053              
- Misses       1361     1370       +9     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.