Cloud Hypervisor used to reject large VM configs over HTTP

The old cap was the HTTP crate’s Firecracker-sized default, not a Cloud Hypervisor choice. ## Notes 247fa0c1a91f (Saravanan D, 2026-08-18). Raise the HTTP request body size limit. The crate rejected bodies above its 51200-byte default before parsing. That default was sized for Firecracker’s microVM API. One disk with 16 queues on a 176 vCPU VM costs about 10 KB of repeated queue affinity; five such disks pushed a vm.create past the cap. New limit is 4 MiB, sized to clear large configs (EPYC Venice 512 threads per socket). Landed on main. Latest release remains v53.0. No GHSA. Not virtio OOB, not a crate bump, not 2c9d17c5 extra-segment slot 0.