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Reading from the DB is "cheap", and the cache hurts the maintainability
of the code.
This removes the CachePolicy and CacheColumn field from TablePolicy.
Instead, a PrimaryKeyColumn has been added to TablePolicy

Instead, have the caller specify which type they want.
This allows us avoid using those ugly std::static_pointer_cast

This makes it easier to scan a row and extract values to variables,
without having to manually pass the column index.
In the likely event we add/remove columns, this will help prevent
regressions as well.

This might need to be reverted when properly addressing files deletion
(while monitoring filesystem or when reloading)
However, as of now, I'm not confident this respect the object ownership
graph anyway

This will avoid random crash due to dangling pointer in case the DB was
released