Java versions for ci (#29320)

* Add test matrix axis files for periodic java testing

* Add properties file defining java versions to use

* We have no openjdk8

* Remove openjdk

Oracle Java and OpenJDK basically only differ in license, so we don't
need to test both.

.ci/java-versions.properties

@@ -0,0 +1,8 @@
+# This file is used with all of the non-matrix tests in Jenkins.
+
+# This .properties file defines the versions of Java with which to
+# build and test Elasticsearch for this branch. Valid Java versions
+# are 'java' or 'openjdk' followed by the major release number.
+
+ES_BUILD_JAVA=java10
+ES_RUNTIME_JAVA=java8

.ci/matrix-build-javas.yml

@@ -0,0 +1,9 @@
+# This file is used as part of a matrix build in Jenkins where the
+# values below are included as an axis of the matrix.
+
+# This axis of the build matrix represents the versions of Java with
+# which Elasticsearch will be built.  Valid Java versions are 'java'
+# or 'openjdk' followed by the major release number.
+
+ES_BUILD_JAVA:
+  - java10

.ci/matrix-java-exclusions.yml

@@ -0,0 +1,14 @@
+# This file is used as part of a matrix build in Jenkins where the
+# values below are excluded from the test matrix.
+
+# The yaml mapping below represents a single intersection on the build
+# matrix where a test *should not* be run.  The value of the exclude
+# key is a list of maps.
+
+# In this example all of the combinations defined in the matrix will
+# run except for the test that builds with java10 and runs with java8.
+# exclude:
+#   - ES_BUILD_JAVA: java10
+#     ES_RUNTIME_JAVA: java8
+
+exclude:

.ci/matrix-runtime-javas.yml

@@ -0,0 +1,10 @@
+# This file is used as part of a matrix build in Jenkins where the
+# values below are included as an axis of the matrix.
+
+# This axis of the build matrix represents the versions of Java on
+# which Elasticsearch will be tested.  Valid Java versions are 'java'
+# or 'openjdk' followed by the major release number.
+
+ES_RUNTIME_JAVA:
+  - java8
+  - java10