chromium shows question marks for more than 1350 costumes

[slyi]

Migrated from scratch-vm as github readme states scratch-vm is outdated. scratchfoundation/scratch-vm#5439

Expected Behavior

All costumes load correctly on chromium https://scratch.mit.edu/projects/1205610476/

Actual Behavior

chromium fails to load more 1350 costumes due limit of 2700 pending network requests and falls back to default unknown webgl texture for network cancelled costumes

Steps to Reproduce

Save a project with more than 1350 costumes

System Details

This occurs on all chromium based browsers (chrome, edge, brave etc...) for sb3 saved projects. Works fine on scrach3.0 win32 app, firefox and webkit.
Scratch VM creates async web request to download the 2048 images but chromium limits pending web requests to NetworkContext::CanCreateLoader returning false. Chrome dislike having more than (kMaxOutstandingRequestsPerProcess = 2700) concurrent loading attempts at a time from a single process (max_loaders_per_process_)
Turbowarp works as batches the downloads. This is a regression from scratch 2.0

Screenshots
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[cwillisf]

See also scratchfoundation/scratch-gui#7111

[cwillisf]

I think we should throttle these loads on "our side" - maybe in scratch-storage. We could use a system similar to the way scratch-desktop avoids loading all items in the media library at once (but generalized rather than being image-specific like the current ScratchImage code).

[slyi]

Sorry yes this is dup of 7111. I wonder if storage can include small images <5kb in the zip like sb2 does. https://scratch.mit.edu/projects/1214387166 as having merged network requests in the zip reduces storage and client latency. It would really help mipmap projects.