[SPARK-19550][BUILD][CORE][WIP] Remove Java 7 support

- Move external/java8-tests tests into core, streaming, sql and remove
- Remove MaxPermGen and related options
- Fix some reflection / TODOs around Java 8+ methods
- Update doc references to 1.7/1.8 differences
- Remove Java 7/8 related build profiles
- Update some plugins for better Java 8 compatibility
- Fix a few Java-related warnings

For the future:

- Update Java 8 examples to fully use Java 8
- Update Java tests to use lambdas for simplicity
- Update Java internal implementations to use lambdas

## How was this patch tested?

Existing tests

Author: Sean Owen <sowen@cloudera.com>

Closes #16871 from srowen/SPARK-19493.

1 files changed, 0 insertions, 2 deletions

diff --git a/common/network-common/src/test/java/org/apache/spark/network/crypto/AuthEngineSuite.java b/common/network-common/src/test/java/org/apache/spark/network/crypto/AuthEngineSuite.java
index 9a186f2113..a3519fe4a4 100644
--- a/common/network-common/src/test/java/org/apache/spark/network/crypto/AuthEngineSuite.java
+++ b/common/network-common/src/test/java/org/apache/spark/network/crypto/AuthEngineSuite.java
@@ -18,10 +18,8 @@
 package org.apache.spark.network.crypto;
 
 import java.util.Arrays;
-import java.util.Map;
 import static java.nio.charset.StandardCharsets.UTF_8;
 
-import com.google.common.collect.ImmutableMap;
 import org.junit.BeforeClass;
 import org.junit.Test;
 import static org.junit.Assert.*;