Support multiple features for PS3I

[zfscgy]

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Docs change / refactoring / dependency upgrade

Motivation and Context / Related issue

The previous version for the PS3I protocol only supports one feature for both the company and partner. If the input file contains more than one data column, those extra columns will be ignored. It is caused by the code in protocol/src/cross_psi only considered the first column in the partner/company's data.

How Has This Been Tested (if it applies)

Changing the file etc/input_partner.csv and etc/input_company.csv to have more than 1 data columns will verify my modifications.

Checklist

• The documentation is up-to-date with the changes I made.
• I have read the CONTRIBUTING document and completed the CLA (see CONTRIBUTING).
• All tests passed, and additional code has been covered with new tests.