Replace internal require-jsapi npm package with an external one

[bmingles]

Once deephaven/deephaven-core#5537 is completed, it should be possible to replace the packages/require-jsapi sub package with whatever package gets created as part of that issue. This assumes it meets the following criteria:

1. npm package handles providing the jsapi as a commonjs module
2. Issues that currently require polyfilling DOM apis have been addressed
3. npm package can provide DHC + DHE jsapis from a given server url