test/helper should be replaced with openzeppelin-test-helpers

[leekt]

I'm submitting a...

[ ] Regression (a behavior that used to work and stopped working in a new release)
[ ] Bug report  
[ ] Performance issue
[x] Feature request
[ ] Documentation issue or request
[ ] Other... Please describe:

Current behavior

currently, vvisp init generates test/helpers folder which is from older version of openzeppelin
since openzeppelin-test-helper module is very useful and has more features, it would be better for vvisp to use this.

Expected behavior

package.json includes "openzeppelin-test-helpers"
no more test/helpers
since just adding this will produce a lot of errors,
truffle has to be upgraded to version 5 or up

Minimal reproduction of the problem with instructions

What is the motivation / use case for changing the behavior?

Environment

vvisp version: X.Y.Z


Environment:
- Node version:
- Operating system:

Others:

[JhChoy]

It was closed with #85