PERF: Panel.shift vs 0.13.1
related: https://github.com/pydata/pandas/pull/6605

```
panel_shift                                  | 263.2827 |   0.0746 | 3528.0756 |
-------------------------------------------------------------------------------
Test name                                    | head[ms] | base[ms] |  ratio   |
-------------------------------------------------------------------------------

Ratio < 1.0 means the target commit is faster then the baseline.
Seed used: 1234

Target [e84efe5] : Merge pull request #6825 from cpcloud/replace-dict-vbenches

BENCH: add vbench for issue 6697
Base   [d10a658] : RLS: set released to True. v0.13.1
```
