fuzz-tests: Make `fuzz-bolt12-offer-decode` roundrip

[Chand-ra]

Changelog-None: Currently, the BOLT #12 offer parsing test only tests the offer decoding function. Add a test for the encoding function as well by making the test roundtrip.

Checklist

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• [x] The changelog has been updated in the relevant commit(s) according to the guidelines.
• [x] Tests have been added or modified to reflect the changes.
• [x] Documentation has been reviewed and updated as needed.
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[madelinevibes]

HI @Chand-ra it seems this one got lost for 25.12, is there an open issue that this PR solves? or if just for CI. I have added it to the milestone for our release early 2025. It will need to be reviewed still!!

[Chand-ra]

HI @Chand-ra it seems this one got lost for 25.12, is there an open issue that this PR solves? or if just for CI.

Hey @madelinevibes, no this PR does not address any open issue.

It is an improvement to an existing fuzz test and is meant to better help in catching regressions in the future. So yes, I suppose it is 'just for CI'.

I have added it to the milestone for our release early 2025. It will need to be reviewed still!!

Makes sense.

[madelinevibes]

HI @Chand-ra it seems this one got lost for 25.12, is there an open issue that this PR solves? or if just for CI.

Hey @madelinevibes, no this PR does not address any open issue.

It is an improvement to an existing fuzz test and is meant to better help in catching regressions in the future. So yes, I suppose it is 'just for CI'.

I have added it to the milestone for our release early 2025. It will need to be reviewed still!!

Makes sense.

great, thanks! can you please rebase before we review?

[Chand-ra]

great, thanks! can you please rebase before we review?

Done!