[JS] Run less comprehensive every-commit build, relegate multi-target builds perhaps to nightlies

[asfimport]

The JavaScript CI build is taking 25-30 minutes nowadays. This could be abbreviated by testing fewer deployment targets. We obviously still need to test all the deployment targets but we could do that nightly instead of on every commit

Reporter: Wes McKinney / @wesm

_{Note: This issue was originally created as ARROW-6759. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
[~paul.e.taylor] for ideas about how to do this in a not-annoying way. Setting up a nightly build is not a big deal

[asfimport]

Paul Taylor / @trxcllnt:
Yeah no sweat, we can change the ci/travis_script_js.sh build and test commands to only test the UMD builds. Historically these have the most issues since they're minified, so if they pass everything should pass:

npm run build -- -m umd -t es5 -t es2015 -t esnext
npm test -- -m umd -t es5 -t es2015 -t esnext

[asfimport]

Wes McKinney / @wesm:
GHA is taking about 25min but as it's running more promptly there seems less urgency to address this for now