Improvements to bundling.

[kitsonk]

Moves to using a minimal System loader for bundles generated by Deno. TypeScript in 3.8 will be able to output TLA for modules, and the loader is written to take advantage of that as soon as we update Deno to TS 3.8.

System also allows us to support import.meta and provide more ESM aligned assignment of exports, as well as there is better handling of circular imports.

The loader is also very terse versus to try to save overhead.

Also, fixed an issue where abstract classes were not being rexported.

It is worth noting that this cannot be used for the internal snapshot bundles, because it turns the whole instantiation process into an async process which executes out of turn, which causes some problems in setting up the runtime environment. The long term plan though for the snapshots is not to use a "bundle" at all, but instead to inject each module into the isolate.

Fixes #2553
Fixes #3559
Fixes #3751
Fixes #3825
Refs #3301

[bartlomieju]

LGTM, I defer to @ry to land

[ry]

Looks good.

It would be useful to have the test case from #3825 in the integration tests. (Note we already have //cli/tests/circular1.js, maybe that can be reused...)

[ry]

Oops, I tried removing bundle_loader.js but it's used by mksnapshot_bundle... I wonder if mksnapshot_bundle couldn't also use this new system bundler?

[kitsonk]

@ry no... mentioned in the comments above:

It is worth noting that this cannot be used for the internal snapshot bundles, because it turns the whole instantiation process into an async process which executes out of turn, which causes some problems in setting up the runtime environment. The long term plan though for the snapshots is not to use a "bundle" at all, but instead to inject each module into the isolate.

In particular, the way we deal with Deno.core caused no end to problems when the bundle instantiated modules asynchronously. I know @bartlomieju tried to rework it to just inject each individual module, that would be better, but I know he ran into issues there too. I know it is a small bit of "duplication" but I think it is better to live with it for a period of time, too.

I will add a test case for #3825.

[ry]

LGTM - thanks kitson!