feat(vmm): added one-shot

[Leechael]

This PR proposes adding a flag dstack-vmm --one-shot <path_to_vm_configuration.json> that allows starting a CVM without launching the supervisor daemon and dstack-vmm daemon, which can be useful for QEMU debugging or benchmarking.

Example output:

$ ~/meta-dstack/dstack/target/release/dstack-vmm -c ~/meta-dstack/build/dev-0.5.1/vmm.toml --one-shot vm_config.json
# Allocated CID: 1000 (found 27 existing QEMU VMs with CIDs: [80001, 1009, 1011, 1007, 1008, 22016, 1001, 1003, 80003, 1002, 1004, 1005, 1006, 22001, 22002, 22003, 22004, 22005, 22006, 22007, 22009, 22011, 22012, 22013, 22014, 80006, 80007])
# One-shot VM execution mode
# Configuration: vm_config.json
# Working directory: /home/leechael/test-app/dstack-oneshot-test-dumps-1754984378
# Compose hash: 7f1b6e01c2af9a98e82b9625d3d16a17c08d907a90c9884a6ad0ce36fea849d7
# App ID: 095ec7fe60d7b7832d1aefd5830627d275cf756b
# VM ID: 84f2fec2-8e4c-4faf-b601-0794aaa63e4b
#
# QEMU Command:
/usr/bin/qemu-system-x86_64 -accel kvm -cpu host -nographic -nodefaults -chardev pty,id=com0,path=/home/leechael/test-app/dstack-oneshot-test-dumps-1754984378/serial.pty,logfile=/home/leechael/test-app/dstack-oneshot-test-dumps-1754984378/serial.log -serial chardev:com0 -bios /home/leechael/meta-dstack/build/dev-0.5.1/images/dstack-dev-0.5.3/ovmf.fd -kernel /home/leechael/meta-dstack/build/dev-0.5.1/images/dstack-dev-0.5.3/bzImage -initrd /home/leechael/meta-dstack/build/dev-0.5.1/images/dstack-dev-0.5.3/initramfs.cpio.gz -drive file=/home/leechael/meta-dstack/build/dev-0.5.1/images/dstack-dev-0.5.3/rootfs.img.verity,if=none,id=hd0,format=raw,readonly=on -device virtio-blk-pci,drive=hd0 -drive file=/home/leechael/test-app/dstack-oneshot-test-dumps-1754984378/hda.img,if=none,id=hd1 -device virtio-blk-pci,drive=hd1 -netdev user,id=net0,net=10.0.2.0/24,dhcpstart=10.0.2.10,restrict=no -device virtio-net-pci,netdev=net0 -machine q35,kernel-irqchip=split,confidential-guest-support=tdx,hpet=off -object tdx-guest,id=tdx,mrconfigid=AX8bbgHCr5qY6CuWJdPRahfAjZB6kMmISmrQzjb+qEnXAAAAAAAAAAAAAAAAAAAA -device vhost-vsock-pci,guest-cid=1000 -virtfs local,path=/home/leechael/test-app/dstack-oneshot-test-dumps-1754984378/shared,mount_tag=host-shared,readonly=on,security_model=mapped,id=virtfs0 -smp 1 -m 2048M -append console=ttyS0 init=/init panic=1 systemd.unified_cgroup_hierarchy=0 net.ifnames=0 biosdevname=0 mce=off oops=panic pci=noearly pci=nommconf random.trust_cpu=y random.trust_bootloader=n tsc=reliable no-kvmclock dstack.rootfs_hash=f2f8c1df568aff0caf1fa6531b3904895b908d38f1c0f9ab91849c7b45515a6d dstack.rootfs_size=150847488
# Executing QEMU...

[kvinwang]

My concern to this PR.

• If there is already a dstack-vmm running, why not just use vmm-cli.py to create a initial stopped VM. maybe an additional RPC for the qemu args is OK?
• Part of one_shot.rs and validation.rs feels hard to maintain.

[kvinwang]

LGTM