Allow widening the foreign key compatibility criteria

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ForeignKey.AreCompatible requires that the foreign and principal keys' CLR properties correspond exactly. While SQL Server is indeed very strict about that, other database support wider foreign key types pointing to narrower principal keys.

On SQL Server:

CREATE TABLE posts (id INT PRIMARY KEY);
CREATE TABLE polls (post_id BIGINT REFERENCES posts(id));

... errors with Column 'posts.id' is not the same data type as referencing column 'polls.post_id' in foreign key 'FK__polls__post_id__5165187F'..

However, the same DDL works fine on PG and Sqlite. We could allow some sort of provider hook that determines whether the properties types are compatible.

Originally flagged by @jessicah in npgsql/efcore.pg#1515

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Duplicate of #19793

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Although it is possible to make EF Core support different types for principal and foreign keys, that's likely quite difficult to do. On the other hand, as specified in #19793, it's possible to simply specify the different store type in the model.

@jessicah although this wouldn't unblock the scaffolding scenario, try to simply define your foreign key as an INT in your model (instead of BIGINT) and everything should work.