Feature request: facadeModuleId in metafile outputs

[yyx990803]

When building a multi-entry bundle with splitting: true, it is often necessary to map output chunks to their original entry modules. Currently, the metafile doesn't provide enough information to do this 100% accurately because two output chunks may contain the same inputs module (if entry B transitively imports entry A). What I am doing right now is checking which output chunk has the same ending sub path segments with the input modules, but this can potentially yield false positives if the paths happen to collide.

Rollup entry chunks contains a facadeModuleId property which points to the original entry module that this chunk was created from. It would be nice to have something similar in esbuild's metafile outputs.

[yyx990803]

FYI for anyone else having similar needs: I've found a way to work around this by using custom entry point names, then using a plugin to resolve and load the entry points in a separate namespace. This keeps the name of the entry points (instead of the file system paths) so esbuild will generate a flat output structure with controlled filenames instead.