Further improvements and savings in Jenkins pipeline (#5904)

* Publish artifacts only on the master and release branches

* Build CUDA only for Compute Capability 7.5 when building PRs

* Run all Windows jobs in a single worker image

* Build nightly XGBoost4J SNAPSHOT JARs with Scala 2.12 only

* Show skipped Python tests on Windows

* Make Graphviz optional for Python tests

* Add back C++ tests

* Unstash xgboost_cpp_tests

* Fix label to CUDA 10.1

* Install cuPy for CUDA 10.1

* Install jsonschema

* Address reviewer's feedback

tests/ci_build/deploy_jvm_packages.sh

@@ -20,16 +20,5 @@ cd jvm-packages
 # Deploy to S3 bucket xgboost-maven-repo
 mvn --no-transfer-progress package deploy -P release-to-s3 -Dspark.version=${spark_version} -DskipTests
 
-# Compile XGBoost4J with Scala 2.11 too
-mvn clean
-# Rename artifactId of all XGBoost4J packages with suffix _2.11
-sed -i -e 's/<artifactId>xgboost\(.*\)_[0-9\.]\+/<artifactId>xgboost\1_2.11/' $(find . -name pom.xml)
-# Modify scala.version and scala.binary.version fields
-sed -i -e 's/<scala\.version>[0-9\.]\+/<scala.version>2.11.12/' $(find . -name pom.xml)
-sed -i -e 's/<scala\.binary\.version>[0-9\.]\+/<scala.binary.version>2.11/' $(find . -name pom.xml)
-
-# Re-build and deploy
-mvn --no-transfer-progress package deploy -P release-to-s3 -Dspark.version=${spark_version} -DskipTests
-
 set +x
 set +e

tests/ci_build/win64_conda_env.yml

@@ -0,0 +1,18 @@
+name: win64_env
+channels:
+- conda-forge
+dependencies:
+- python=3.7
+- numpy
+- scipy
+- matplotlib
+- scikit-learn
+- pandas
+- pytest
+- python-graphviz
+- boto3
+- hypothesis
+- jsonschema
+- pip
+- pip:
+  - cupy-cuda101