Stacked on https://dagster.phacility.com/D7418.
A handful of changes to enable (and take the first couple steps in) bundle splitting.
- Use __webpack_public_path__ to set a path prefix dynamically. This will be used for all dynamically loaded bundles. The file that sets this value must be the first import in the entry file. I added comments to that effect.
- Last time I tried splitting the bundle, dynamic bundles failed to load in the path-prefix case, because they did not take the prefix into account (https://github.com/dagster-io/dagster/issues/3696). With this change, this issue is fixed.
- Change how we set the path prefix in the DOM. This approach is more in line with how we're handling other preloaded values.
- Split InstanceRoot and WorkspaceRoot as a first step. This ensures that the approach works, and is a reasonable first place to split the bundle anyway.