Major Changes in microvm.nix

Unreleased: `main` branch

microvm-virtiofsd@.service now starts the multiple virtiofsd instances through supervisord.
The host module allows configuration of microvm.virtiofsd.inodeFileHandles and microvm.virtiofsd.threadPoolSize now.
Add the alioth VMM
Fixes for the stratovirt VMM
New volume image files will be created with truncate instead of fallocate, saving disk space.

tap interfaces are now multi-queue when running with more than one VCPU. Update your host!
The host module enables Kernel Samepage Merging by default.
qemu can run non-native systems by using its Tiny Code Generator instead of KVM.
SSH deployment scripts are added as config.microvm.deploy.rebuild
qemu defaults to the microvm machine model now as it supports PCI, USB, and ACPI by now. Set microvm.qemu.machine = "q35" if this breaks for you.
The NixOS hardened profile can be used by falling back to squashfs.
Runners execute the hypervisor with a process name of microvm@$NAME
We no longer let environment.noXlibs default to true
Breaking: the microvm user is no longer in the disk group for security reasons. Add users.users.microvm.extraGroups = [ "disk" ] to your config to restore the old behavior.

cloud-hypervisor replaces rust-hypervisor-firmware with direct kernel+initramfs loading.
The microvm module now optimizes the NixOS configuration for size.
crosvm now supports macvtap interfaces.
The option microvm.qemu.bios has been dropped again for simplicity reasons.

qemu boots fast with the shipped SeaBIOS if after both SATA and the network interface option ROM (iPXE) have been disabled.
microvm.kernelParams always copy boot.kernelParams
firecracker is no longer launched through firectl.
Networking example documentation has been split into multiple scenarios.
Vsock support has been added for Hypervisors that connect them to the Linux host's AF_VSOCK: qemu, crosvm, and kvmtool.
Our packages and overlay include the unstable version of waypipe, featuring Vsock support.
Add support for the old command-line parameter syntax that returned with cloud-hypervisor 36.0.

Stop building a custom kernel by booting the NixOS kernel with an initrd.
New Hypervisor: stratovirt by Huawei
Support fully declarative MicroVMs that are part of the host's NixOS configuration. No Flakes required!
We use squashfs-tools-ng now.
The microvm-console script has been removed because pty console setup was too cumbersome to maintain across all hypervisors.
microvm.storeDiskType defaults to "erofs" now for higher runtime performance.