* upstream/master: (43 commits)
  bump version to 2021.03.0
  Bump minimum version of distributed (dask#7328)
  Fix `percentiles_summary` with `dask_cudf` (dask#7325)
  Temporarily revert recent Array.__setitem__ updates (dask#7326)
  Blockwise.clone (dask#7312)
  NEP-35 duck array update (dask#7321)
  Don't allow setting `.name` for array (dask#7222)
  Use nearest interpolation for creating percentiles of integer input (dask#7305)
  Test `exp` with CuPy arrays (dask#7322)
  Check that computed chunks have right size and dtype (dask#7277)
  pytest.mark.flaky (dask#7319)
  Contributing docs: add note to pull the latest git tags before pip installing Dask (dask#7308)
  Support for Python 3.9 (dask#7289)
  Add broadcast-based merge implementation (dask#7143)
  Add split_every to graph_manipulation (dask#7282)
  Typo in optimize docs (dask#7306)
  dask.graph_manipulation support for xarray.Dataset (dask#7276)
  Add plot width and height support for Bokeh 2.3.0 (dask#7297)
  Add numpy functions tri, triu_indices, triu_indices_from, tril_indices, tril_indices_from (dask#6997)
  Remove "cleanup" task in dataframe on-disk shuffle. The partd directory (dask#7260)
  ...