refactor(routingprocessor): use MoveTo instead of CopyTo

[pmalek-sumo]

Description: use MoveTo instead of CopyTo

Link to tracking Issue: N/A

Testing: existing UTs

Documentation:

$ go test -v -count 1 -run ^$ -bench Benchmark -benchmem -count 1 .
goos: darwin
goarch: amd64
pkg: github.com/open-telemetry/opentelemetry-collector-contrib/processor/routingprocessor
cpu: Intel(R) Core(TM) i9-9980HK CPU @ 2.40GHz
Benchmark_MetricsRouting_ResourceAttribute
Benchmark_MetricsRouting_ResourceAttribute-16            1463461               813.2 ns/op           688 B/op         16 allocs/op
PASS
ok      github.com/open-telemetry/opentelemetry-collector-contrib/processor/routingprocessor    2.432s
$ go test -v -count 1 -run ^$ -bench Benchmark -benchmem -count 1 .
goos: darwin
goarch: amd64
pkg: github.com/open-telemetry/opentelemetry-collector-contrib/processor/routingprocessor
cpu: Intel(R) Core(TM) i9-9980HK CPU @ 2.40GHz
Benchmark_MetricsRouting_ResourceAttribute
Benchmark_MetricsRouting_ResourceAttribute-16            1694242               702.0 ns/op           592 B/op         15 allocs/op
PASS
ok      github.com/open-telemetry/opentelemetry-collector-contrib/processor/routingprocessor    2.328s

[jpkrohling]

Looks good, I have a similar change as part of #7771 but I think @dmitryax had some concerns. What do you think about using MoveTo here, @dmitryax?

[dmitryax]

No, this is different. I believe we can switch to MoveTo here, because it's called only once per each ResourceMetrics object, and we don't need to preserve the original pdata.Metrics object. But it's not the case for #7771.