Integrate new `@sap/cds-common-content` package

[chgeo]

• Needs @sap/cds 6.4
• Deleted now superfluous csv files

[chgeo]

I have split the UPSERT test in a dedicated PR https://github.com/SAP-samples/cloud-cap-samples/pull/521, so that it can be tested w/o using the common-content package at the same time.

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