hakurei 0.2.0

API Changes:
- Remove `cover` field from `hst/container`.
- Remove `symlink` field from `hst/container`.
- Field `data` has been renamed to `home`.
- field `dir` has been removed since it is made redundant by `filesystem`.
- All pathname fields now take the `*container.Absolute` type. Does not break json.
- The `filesystem` field now accepts many types of supported filesystems.
- Container root behaviour is now configured through the `filesystem` field.
- Autoetc behaviour is now accessible through a special `bind` type `filesystem`.
- Autoroot behaviour is now accessible through a special `bind` type `filesystem`.
- The enablement flags are now represented in `json` as boolean fields.
- Net and Abstract fields have been renamed. Does not break `json`.
- Autoroot prefix has been removed.
- Share path now uses hsu userid.

Fixes:
- Unexport internal `container` state.
- Package `container` no longer attempts to look up executable file from name.
- Set up acl on X server socket.
- Check `container` setup op equivalence by value.
- Validate `container` setup ops early.

Enhancements:
- Export mount string constants.
- Export FHS pathname constants
- Mount mqueue as part of `/dev`.
- Mount container `/dev` read only.
- High-level API for overlay mounts in `container`.
- The `hakurei show` command now exposes more information.
- Optionally isolate host abstract UNIX domain sockets via landlock.
- Ptrace protection via Yama LSM.

Internal:
- Move `tmpfs` pathname prefixing to caller.
- Expose interactive testing vm for tracing.
- Reduce noise in non-verbose tests and test failures.
- CAP_DAC_OVERRIDE is now raised for `container/init`.
- Container setup ops are now able to share global state.
- Enforce nonrepeatable autoetc and autoroot.
- Container now spawns on a locked thread tied to its lifecycle.
- Full test coverage has been achieved in `container` setup code.
- NixOS module config validation is now implemented via `hakurei show`.
- Output of initial hakurei run in vm tests is no longer discarded.
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