Add MySQL port to Hyperdrive binding

[prydt]

This change makes Hyperdrive's magic connection string port match the database the user is using. This does not and should not change functionality, it just changes the user visible port to avoid confusion.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.60%. Comparing base (4d7ea26) to head (a1ed9ab).
⚠️ Report is 31 commits behind head on main.

Files with missing lines	Patch %	Lines
src/workerd/api/hyperdrive.c++	0.00%	4 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6195      +/-   ##
==========================================
- Coverage   70.63%   70.60%   -0.04%     
==========================================
  Files         413      413              
  Lines      109873   109971      +98     
  Branches    18098    18121      +23     
==========================================
+ Hits        77614    77643      +29     
- Misses      21454    21519      +65     
- Partials    10805    10809       +4     

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