Add FromSql and ExecuteSql accepting FormattableString

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As discussed offline, we're going to add these, which are identical to FromSqlInterpolated/ExecuteSqlInterpolated. FormattableString is safe from SQL injection attacks, so we generally want to guide users towards doing raw SQL with it, and suffix-less "default" methods would likely be used more by new users etc..

We also considered renaming FromSqlRaw to FromSqlUnsafe to make it clearer that these methods should be used with care, and also removing FromSqlInterpolated/ExecuteSqlInterpolated (obsoleting first). We won't do this since the team decided that the breaking change isn't worth it.