Use chloggen go tool for managing the changelog

[joaopgrassi]

Fixes #617

Changes

Today it's very cumbersome how the changes in CHANGELOG.md are managed. It's frustrating for all parties:

• Contributors have constant merge conflicts in their PRs
• The process of releasing a new semconv version is very manual, maintainers have to move things around in the markdown file and it's very error-prone
• When we release a new version, opened PRs that already had changes in the changelog may be misplaced and unless someone looks for it, it's easy to miss. See: Improvements for AWS/ECS attributes #597 (comment)

This PR attempts to add and use the chloggen tool, the same way that the collector repos use.

I also did a revamp in the contributing guide and tried to make it as friendly as possible for new contributors.

Note: It is still missing the new steps for making a release, but once this is merged I will also update that.

[joaopgrassi]

Here is a preview of a CHANGELOG file generated by the new tool (with dummy changelog entries)

vTODO

🛑 Breaking changes 🛑

• DB: test (Tooling: Can we come up with another way to edit CHANGELOG and schema-next.yaml? #617)
  Breaking changes in db semconv..

💡 Enhancements 💡

• HTTP: test (Tooling: Can we come up with another way to edit CHANGELOG and schema-next.yaml? #617)
  Add new changelogs

🧰 Bug fixes 🧰

• HTTP: test (Tooling: Can we come up with another way to edit CHANGELOG and schema-next.yaml? #617)
  Fix wrong attribute...

[jsuereth]

Generally LGTM, just a question on some of the CONTRIBUTING refactoring.

[joaopgrassi]

Moved this out of draft, as folks may not look at things in that state. I still need to work on the automated checks.

Update: GH Workflow to check the for the changelog entries is there now.

[trisch-me]

thanks for working on it!

[lmolkova]

Thank you!