incus: add per-instance lxcfs and disk hot-resize

[adamcstephens]

Description of changes

These two features were added in 6.4 and 6.5.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 24.11 Release Notes (or backporting 23.11 and 24.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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[adamcstephens]

per-instance lxcfs failing with

lxc container 20240908152654.163 ERROR    utils - ../src/lxc/utils.c:run_buffer:571 - Script exited with status 32
lxc container 20240908152654.163 ERROR    conf - ../src/lxc/conf.c:lxc_setup_rootfs_prepare_root:3492 - Failed to run pre-mount hooks
lxc container 20240908152654.163 ERROR    conf - ../src/lxc/conf.c:lxc_setup:3871 - Failed to setup rootfs
lxc container 20240908152654.163 ERROR    start - ../src/lxc/start.c:do_start:1273 - Failed to setup container "container"
lxc container 20240908152654.163 ERROR    sync - ../src/lxc/sync.c:sync_wait:34 - An error occurred in another process (expected sequence number 3)
lxc container 20240908152654.180 WARN     network - ../src/lxc/network.c:lxc_delete_network_priv:3674 - Failed to rename interface with index 0 from "eth0" to its initial name "vethbf433c9f"
lxc container 20240908152654.181 ERROR    start - ../src/lxc/start.c:__lxc_start:2114 - Failed to spawn container "container"
lxc container 20240908152654.181 WARN     start - ../src/lxc/start.c:lxc_abort:1037 - No such process - Failed to send SIGKILL via pidfd 18 for process 5456
lxc container 20240908152654.181 ERROR    lxccontainer - ../src/lxc/lxccontainer.c:wait_on_daemonized_start:837 - Received container state "ABORTING" instead of "RUNNING"
lxc 20240908152654.280 ERROR    af_unix - ../src/lxc/af_unix.c:lxc_abstract_unix_recv_fds_iov:218 - Connection reset by peer - Failed to receive response
lxc 20240908152654.280 ERROR    commands - ../src/lxc/commands.c:lxc_cmd_rsp_recv_fds:128 - Failed to receive file descriptors for command "get_init_pid"

[adamcstephens]

disk hot-resize failing with

machine # [   53.512654] incusd[872]: time="2024-09-08T15:06:08Z" level=warning msg="Could not apply quota because disk is in use, deferring until next start" device=root driver=disk instance=instance1 project=default

[adamcstephens]

hot-disk resize is storage backend dependent and not supported on disk driver. skipping adding a test.
lxcfs works as intended and is handled in #373920