Gluonts

Backporting fixes:
- itertools.select. 2426 by jaheba
- Fix dataclass handling of member inheritance. 2492 by jaheba
- Fix: sort dataset keys in error message when importing non-existing dataset 2497 by lostella
- Fix DateSplitter for multiples of base frequencies 2500 by lostella
- Fix docstrings according to docformatter 2501 by lostella
- Add examples to docstring for periods_between 2504 by lostella
- Cap numpy compatibility in mxnet extra requirements 2506 by lostella
- Pin docformatter version. 2507 by jaheba
- Docs: Fix install instructions. 2508 by jaheba

What's Changed

* Backports for v0.11.5. by jaheba in https://github.com/awslabs/gluonts/pull/2491


**Full Changelog**: https://github.com/awslabs/gluonts/compare/v0.11.4...v0.11.5

Backports:

* Fix pandas issue with inferring start of X frequency. (2462 by jaheba)

Backporting fixes:
- Add test cases for PandasDataset, fix missing assertion (2453 by lostella)
- Speed up PandasDataset further (2441 by lostella)
- Fix MANIFEST.in (2456 by lostella)

Backporting fixes:
- Add test cases for PandasDataset, fix missing assertion (2453 by lostella)
- Speed up PandasDataset further (2441 by lostella)
- Fix MANIFEST.in (2456 by lostella)

Backporting fixes:
- Fix rotbaum random seed and num_samples argument. (2408 by sighellan)
- Hierarchical: Make sure the input S matrix is of right dtype (2415 by rshyamsundar)
- Mypy fixes (2427 by jaheba)
- Speed up PandasDataset for long dataframes (2435 by lostella)
- Fix frequency inference in PandasDataset (2442 by lostella)
- Tests: Change Python versions. (2448 by jaheba)