Remove PR# from changelogs

[emmyoop]

Part of https://github.com/dbt-labs/dbt-core/issues/6332 - Removed PR from all changelog kinds except Dependencies and Security since those are bot generated by dependabot and snyk. Also adds support for multiple issues in a single changelog so features can have a single changelog with multiple issues.

1. Update .changie.yaml to only use issue for all kinds (except Dependency & Security - use PRs only there). Also add support for multiple issues within a single changelog.
2. Update change body in bot-changelog.yml to no longer include placeholder issue number. Also update kind in this file to be Dependencies instead of [Dependency] to match changie.yaml - this was an existing bug
3. Existing changelog yaml files do not need to be modified to remove the extra fields. They will be ignored on generation. However the kind in the Dependency changelogs (if any exxist) do need to updated to have be kind: "Dependency"

Related dbt-core PR: https://github.com/dbt-labs/dbt-core/pull/6374

These changes should be the same as the dbt-core PR with the exception of the Docs kinds as this repo does not have that kind.

General Cleanup: Remove the Docs kind from .changie.yaml or reformat it if appropriate. As is, it points to changes from the dbt-docs repo.

[emmyoop]

The adapter PRs would be good reference for this and exactly what needs to be done: https://github.com/dbt-labs/dbt-bigquery/pull/480