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ARROW-8153: [Packaging] Update the conda feedstock files and upload artifacts to Anaconda

The windows builds were failing, so the feedstock files must be updated.

Under the same hat add support for uploading the produced artifacts to Anaconda labeled as nightly.

The uploaded conda packages are available under https://anaconda.org/ursa-labs/repo

Closes #6658 from kszucs/anaconda

Lead-authored-by: Krisztián Szűcs <szucs.krisztian@gmail.com>
Co-authored-by: Sutou Kouhei <kou@clear-code.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>