fix(meshmetric): add missing timestamp in mapper (backport of #10966)

[kumahq]

Automatic cherry-pick of #10966 for branch release-2.4

Generated by action

cherry-picked commit 4045726
⚠️ ⚠️ ⚠️ Conflicts happened when cherry-picking! ⚠️ ⚠️ ⚠️

On branch release-2.4
Your branch is up to date with 'origin/release-2.4'.

You are currently cherry-picking commit 404572688.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by us:   app/kuma-dp/pkg/dataplane/metrics/metrics_format_mapper.go
	deleted by us:   app/kuma-dp/pkg/dataplane/metrics/metrics_format_mapper_test.go
	deleted by us:   app/kuma-dp/pkg/dataplane/metrics/metrics_producer.go
	deleted by us:   app/kuma-dp/pkg/dataplane/metrics/testdata/otel/counter.golden.json
	deleted by us:   app/kuma-dp/pkg/dataplane/metrics/testdata/otel/counter.in
	deleted by us:   app/kuma-dp/pkg/dataplane/metrics/testdata/otel/gauge.golden.json
	deleted by us:   app/kuma-dp/pkg/dataplane/metrics/testdata/otel/histogram.golden.json
	deleted by us:   app/kuma-dp/pkg/dataplane/metrics/testdata/otel/summary.golden.json

no changes added to commit (use "git add" and/or "git commit -a")

[slonka]

MeshMetric was introduced in 2.6.0