BUG: Fixed DataFrameGroupBy.transform with numba returning the wrong order with non increasing indexes #57069
- [X] closes #57069
- [X] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests) if fixing a bug or adding a new feature
- [X] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [X] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
- [X] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

DataFrameGroupBy.transform with numba was returning the wrong order unless the index was monotonically increasing due to the transformed results not being correctly reordered. 
Fixed the test "pandas/tests/groupby/transform/test_numba.py::test_index_data_correctly_passed" to expect the correct order in the result.
Added a test "pandas/tests/groupby/transform/test_numba.py::test_index_order_consistency_preserved" to test DataFrameGroupBy.transform with engine='numba' with a decreasing index.
Thanks @andremcorreia 