Update DeepHavenJsApiLinker to allow exporting GWT JsTypes as ES6 module

[vegegoku]

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[vegegoku]

I have read the CLA Document and I hereby sign the CLA

[mofojed]

Going to create tickets for some additional things, such as publishing these as a package in npmjs (e.g. @deephaven/jsapi and/or @deephaven/jsapi-internal).

Whitespacing is inconsistent in many of the new lines in these examples.

[mofojed]

Spoke with @niloc132 about this, and the change looks good as a halfway point, however it makes consuming the library more difficult. Ultimately suggest we keep this as a fork or a separate branch until we have the full thing exported as a module (dh-internal as well) and published to npmjs.

The reason why this is difficult is because the Web UI still needs to load it remotely from the server. Currently, it's just doing a regular script tag with type text/javascript, which add dh to the global namespace: https://github.com/deephaven/web-client-ui/blob/1d10956499cd451145e704690bc8f2d5cfb6a786/packages/code-studio/public/index.html#L41
There is then the jsapi-shim which pulls dh from the global namespace, which we use from our modules to be able to import the jsapi: https://github.com/deephaven/web-client-ui/blob/1d10956499cd451145e704690bc8f2d5cfb6a786/packages/jsapi-shim/src/dh.ts#L11

That shim only works if dh is already on the global namespace. However, when importing a script using type="module", it defers loading until after the page is already loaded. So we'd need to defer the web UIs startup entirely to wait for the dh module to import before we load the rest of our code. It's simply a pain in the butt, and doesn't really have any benefits yet at this point. We also can't just do import dh from './dh-core.js', since it's loading from a remote address (e.g. we need to do <script type="module" src="http://localhost:10000/jsapi/dh-core.js">). As a consumer of the library, this halfway point is actually more difficult to use/consume (even though it is a step in the right direction).

Once dh-internal is also a module, and they're both published to npmjs, theoretically should be able to change jsapi-shim to just:

import dh from '@deephaven/jsapi';
export default dh;

And everything should work. (We could also just change all our imports from import dh from '@deephaven/jsapi-shim' to import dh from '@deephaven/jsapi', but by keeping the shim we can actually have the same code work on both Enterprise and Community until we get Enterprise to export as a module as well).

So, I approve these changes, but please don't merge them to main, and keep a separate long running branch for this development :).

[deephaven-internal]

Labels indicate documentation is required. Issues for documentation have been opened:

How-to: https://github.com/deephaven/deephaven.io/issues/2180
Conceptual: https://github.com/deephaven/deephaven.io/issues/2181
Reference: https://github.com/deephaven/deephaven.io/issues/2179
Blog: https://github.com/deephaven/deephaven.io/issues/2178