Update Jackson to 2.21.5 for security findings

Debezium main uses Jackson 2.21.2 through `version.jackson` and `version.jackson.databind` in the root POM.

I scanned the Debezium Server nightly image with Wiz CLI v1.31.0-de890c7 on 2026-08-10. The image digest was `sha256:f1a168a7accf69459024730565929b52e619e1c3edc8d7b3c7a372d6570bffc8`.

Wiz reports these Jackson findings:

- CVE-2026-54512 [High]
- CVE-2026-54513 [High]
- CVE-2026-54514 [Medium]
- CVE-2026-54515 [Medium]
- CVE-2026-54516 [Medium]
- CVE-2026-54517 [Medium]
- CVE-2026-54518 [Medium]
- CVE-2026-59888 [Medium]
- CVE-2026-59889 [Medium]
- GHSA-mhm7-754m-9p8w [Medium]

I suggest updating `version.jackson` and `version.jackson.databind` to 2.21.5. `version.jackson.annotations` should stay on 2.21 because this property uses a separate version line.

I tested this version first as Maven property overrides. A clean build for the 20 affected modules passed and Maven resolved Jackson 2.21.5. Unit tests, formatting checks, checkstyle, architecture tests, and Revapi passed in this build.

I also applied the two property changes to the latest main commit `4d5cc38180816ec2ddfe184d968ad4aa254098c7`. The full 62-module `clean install -Dquick` build passed in 2 minutes and 3 seconds. The quick profile skips the normal unit and integration tests, but the build checks, architecture tests, and service registration checks completed.

Acceptance criteria:

- Update `version.jackson` and `version.jackson.databind` to 2.21.5.
- Keep `version.jackson.annotations` on 2.21.
- Run the affected core and connector tests.
- Build the Debezium Server image.
- Scan the final image with Wiz CLI and confirm that these Jackson findings are removed.

DBZ #701 and Debezium PR #7124 cover older Jackson work and do not cover this version.