[TASK] Merge dashboard widget service conf to Services.yaml

There is little point extracting single widget
configuration to an own file - we don't split
Services.yaml in any other extension.
Merge DashboardWidgets.yaml into Services.yaml.

Resolves: #103936
Releases: main
Change-Id: I00ba601a57942fc543728c87404f0944a307bf0c
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/84425


Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Benjamin Franzke <ben@bnf.dev>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Benjamin Franzke <ben@bnf.dev>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Stefan Bürk <stefan@buerk.tech>