Serialize decorator data at the end

[yasonk]

Describe your changes

Moving all decorator data to the end in order to enable truncating it later. See issue #1489

Contains a minor refactor to make writing decorator info more direct by reducing interconnected layers of indirection. Also extracted some functions from the Serializer code to make it easer follow.

Checklist before requesting a review

• [x] Repo forked and branch created from next according to naming convention.
• [x] Commit messages and codestyle follow conventions.
• [x] Relevant issues are linked in the PR description.
• [x] Tests added for new functionality. (No new tests)
• [x] Documentation/comments updated according to changes. (No Doc changes)

[yasonk]

Rebased and started signing commits. But I don't think I can sign older commits.

[yasonk]

@PhilippGackstatter I addressed the last 4 comments. Thank you for the great suggestions in all cases!

[PhilippGackstatter]

@yasonk Thanks for the updates and signing commits!

I think just two more things to make CI happy:

• Replace uses of std::iter::from_fn with core::iter::from_fn and import Vec from alloc::vec::Vec instead of std.
• Add an entry in CHANGELOG.md

You can try locally if the no-std build works without issues using make build-no-std.

@plafer Should we go ahead and merge after that or do you want to take another look?

[bobbinth]

@plafer Should we go ahead and merge after that or do you want to take another look?

Let me do a quick review. I'll try to do this on Friday.