Intl NumberFormat v3: Add tests for roundingPriority when all 4 settings are used at the same time (min+max fraction+significant)

[rwaldron]

Suggestion: Add tests for roundingPriority when all 4 settings are used at the same time (min+max fraction+significant)

Originally posted by @sffc in #3334 (comment)

[romulocintra]

@rwaldron I think we can close this one -> #3405

[ptomato]

I understood that another PR was still needed with tests for different values of roundingPriority (#3405 (review))

[rwaldron]

@ptomato I'll let you drive this

[romulocintra]

Related PR #3372