Give every operator the same table to read

### Task Summary

One table for every operator to read: thirty-four columns and fifteen rows, holding a column of every type an operator can ask for and the awkward values each type admits, an empty cell, a zero, a negative, a string that looks like a number, a date at a boundary.

An operator that needs something the table cannot hold, a pair of tables sharing a key or a numeric projection, names a projection of it rather than a fixture of its own, so what every operator reads stays one thing.

Step 8 of 27 in #8325. It reads the `@SampleColumn` annotation, so it needs #8327.