Use PRAGMA defer_foreign_keys instead of PRAGMA foreign_keys when migrating

[ferferga]

This Pull Request changes the use of PRAGMA foreign_keys in SQLite migrations to PRAGMA defer_foreign_keys, which are allowed inside transactionss without any issue.

It's one of the possible fixes for #35871, and I think the best one, since we will use the exact pragma that SQLite wants to be used for transactions, instead of working around it.

I did my best attempt to update the tests as well, but not sure this is how I should do it (since I didn't see any mention to BEGIN TRANSACTION inside the generated SQL in tests.

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[ferferga]

@dotnet-policy-service agree