Update TableFormat metric to TableStructure + fix its computation

[npatki]

Problem Description

This metric is checking the names of the columns as well as the dtypes of the data. The dual-purpose is confusing, especially since (a) it makes the computation more difficult, and (b) there are other metrics that look for the validity of the data.

Let's simplify the metric.

Expected behavior

1. Rename the metric to TableStructure
2. Stop checking for dtypes in the this metric. We only need to check for the column names.
   • We can get rid of the parameter for ignoring dtypes
   • The 'Structure' property in the Diagnostic Report no longer has to compute or pass the parameter in anymore
3. Fix the computation to be

score = (R intersection S) / (R union S)

Where R is the set of real column names and S is the set of synthetic column names.