JS backend CI does not run the testsuite. This is obviously bad, this MR runs the testsuite only for the JS backend. However, this is a stop gap solution until !9515 (merged) is merged into hadrian.
Marking as draft until I mark other tests as broken and figure out why the wasm CI breaks, and do some clean up:
non-JS CI is untouched and passes
JS CI passes
cleanup: in particular superfluous
infos in the CI script