Drop dependency on EF Core internals

[bkoelman]

This fixes a warning in one of the samples when using EF Core 9 (preview 1), to not depend on EF Core internals. The fix also avoids the need for dealing with a breaking change in EF Core 9, and it optimizes to build the model only once at startup.

Furthermore, this PR reduces cohesion by internally depending on IReadOnlyModel instead of IModel.

QUALITY CHECKLIST

• Changes implemented in code
• Complies with our contributing guidelines
• N/A: Adapted tests
• N/A: Documentation updated

[codecov]

Codecov Report

Attention: Patch coverage is 98.03922% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 90.75%. Comparing base (06d6b18) to head (3bf9157).

Files	Patch %	Lines
...ionToSql/DataModel/FromEntitiesDataModelService.cs	75.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@ Coverage Diff @@ ## master #1492 +/- ## ======================================= Coverage 90.74% 90.75% ======================================= Files 344 344 Lines 11003 11006 +3 Branches 1805 1806 +1 ======================================= + Hits 9985 9988 +3  Misses 669 669 Partials 349 349 

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