Backport PR #43468: CI: split Windows Azure tests in half
Backport #43468 to 1.3.x
https://dev.azure.com/pandas-dev/pandas/_build/results?buildId=65945&view=logs&j=7ae4cfe6-c794-57c3-450a-5b4ec49e7feb&t=b053f402-64af-50ba-ae37-4304bce0dbf0, missing some changes. > https://dev.azure.com/pandas-dev/pandas/_build/results?buildId=65945&view=logs&j=7ae4cfe6-c794-57c3-450a-5b4ec49e7feb&t=b053f402-64af-50ba-ae37-4304bce0dbf0, missing some changes.

Actually - the new version has 3.9 tests, but 1.3.x doesn't have them, so had to remove them from the  merge. thanks @Dr-Irv very nice!