chore: clean-up changelog

[julienrbrt]

Description

I was looking for a method to speed up and facilitate the fact of removing entries from the unreleased section of the changelog (like done at each release 1edc60b, 1133b6b, ...)

I used a small script where I moved beforehand the unreleased changelog to CHANGELOG_PENDING.md and left the rest in CHANGELOG.md.

Then ran grep -vxFf $2 $1 > $1.tmp && mv $1.tmp $1 for removing the duplicate lines. ($2 = changelog_pending and $1 = changelog.md)
Afterward, I re-added that changelog pending back in CHANGELOG.md with the proper headers.

As we can see, there were still many duplicates entries from unreleased.
I am working on making the process above just one script, but in the meantime, the changelog can already be cleaned.

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Author Checklist

All items are required. Please add a note to the item if the item is not applicable and
please add links to any relevant follow up issues.

I have...

• included the correct type prefix in the PR title
• added ! to the type prefix if API or client breaking change
• targeted the correct branch (see PR Targeting)
• provided a link to the relevant issue or specification
• followed the guidelines for building modules
• included the necessary unit and integration tests
• added a changelog entry to CHANGELOG.md
• included comments for documenting Go code
• updated the relevant documentation or specification
• reviewed "Files changed" and left comments if necessary
• confirmed all CI checks have passed

Reviewers Checklist

All items are required. Please add a note if the item is not applicable and please add
your handle next to the items reviewed if you only reviewed selected items.

I have...

• confirmed the correct type prefix in the PR title
• confirmed ! in the type prefix if API or client breaking change
• confirmed all author checklist items have been addressed
• reviewed state machine logic
• reviewed API design and naming
• reviewed documentation is accurate
• reviewed tests and test coverage
• manually tested (if applicable)