Verify model roundtrip with HUGR and Guppy tests

[ss2165]

• HUGR validation roundtrips serialisation, add model to this
• Guppy tests can be validated through model
• Check all examples in guppy-integration can run through model
• re-run benchmarks

[zrho]

The validation roundtrip surfaced some bugs and mismatches which have been fixed:

• fix: Import and export JSON metadata on module roots. #2207
• fix: Respect type bounds on local variables when importing. #2206
• feat: Import CFG regions without adding an entry block. #2200
• fix: Panic when an extension name is too long. #2198
• feat!: Remove description on opaque ops. #2197

[zrho]

To be able to debug errors when they come up with the format being used in practice, better error messages are useful (#2260). The PR #2272 improved error messages to some extent and made the error type private so that messages can be improved without breaking changes.

[aborgna-q]

HUGR validation roundtrips serialisation, add model to this

The code doing this is currently commented-out due to shortcomings of the hugr equality checker.
https://github.com/CQCL/hugr/blob/214b8df837537b8ac15c3b60845350c3818a6ac7/hugr-core/src/hugr/validate.rs#L76-L77

We may need to relax the check there, or implement a more intelligent checker (I couldn't find the issue for it?)