Prepack: integrate it with test262-stream

[leobalter]

considering we have the data set from #129 and the test262-harness filter feature, we should work on the integration of it within Prepack

• Add the test262 event stream api #125
• (no issue) publish the integration script
• (no issue) replace Prepack's test262-runner script with the new one using the integration script
• Add frontmatter tags filter on Test262 integration #127
• config file for project #142
• Add a location filter for Test262 integration #128
• Add a features filter on Test262-harness #124

[leobalter]

closing as dupe of #120

[leobalter]

not a dupe, this is a tracker for the actual integration script.