docs: group collection reporting hooks

[LouisDeconinck]

Summary

Move the collection lifecycle reporting hooks into the Collection hooks section so plugin authors can find them with the phase they describe.

Fixes #12658

Verification

• uv run --frozen --with tox --with tox-uv tox -e docs
• git diff --check

Checklist

• Include documentation when adding new features.
• Include new tests or update existing tests when applicable.
• Allow maintainers to push and squash when merging my commits.
• Add text like closes Docs: collection hooks listed under reporting hooks #12658 to the PR description.
• AI assistance was used and the commits include Co-authored-by trailers; the change was human-reviewed and verified.
• Create a new changelog entry in changelog/15000.doc.rst.
• Add yourself to AUTHORS (this is a small documentation fix).

[SemTiOne]

The file name should be 12658.doc.rst.

[LouisDeconinck]

@SemTiOne Done — folded the collection-hooks fragment into changelog/12658.doc.rst and dropped the PR-numbered file. Both notes now live under the issue number.