LibWeb: Features and bug fixes towards getting Ruffle to load once again :^)

[Lubrsi]

This is possible with a few extra hacks (not included in this PR)

• Don't expose ReadableStream so it doesn't use it (fetch doesn't currently setup the stream)
• Commented out some Wasm SIMD validation to use the non-SIMD blob, as I think there's SIMD parsing bugs (get unexpected EOF with the SIMD blob)
• Commented out Wasm validation, as it is extremely slow

Ref issue #17993

[stale[bot]]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed in 7 days if no further activity occurs. Thank you for your contributions!

[awesomekling]

Not stale