Place DATAVECTOR_BASE at end of Jet_v1.h, similar to rel 21.2

We did that in 21.2 as helps with certain cases of specialization after instantiation. Let's have it in master.

@akraszna @manthony @mhodgkin

This merge request affects 1 package:

• Event/xAOD/xAODJet

Adding @akraszna as watcher

added EDM JetEtmiss master review-pending-level-1 labels

CI Result SUCCESS (hash 49cd8ab8)

	Athena	AthSimulation	AthGeneration	AnalysisBase
externals
cmake
make
required tests
optional tests

Full details available on this CI monitor view
Athena: number of compilation errors 0, warnings 0
AthSimulation: number of compilation errors 0, warnings 0
AthGeneration: number of compilation errors 0, warnings 0
AnalysisBase: number of compilation errors 0, warnings 0
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 20149]

added review-approved label and removed review-pending-level-1 label

merged

mentioned in commit a6c0dd91

added sweep:ignore label