Update gradle wrapper to Gradle 6.7 (#62386)

- Ignore Memory Manager thread in Gradle thread filter
- Update gradle wrapper to 6.7 GA release

Author: breskeby

buildSrc/src/main/resources/minimumGradleVersion

@@ -1 +1 @@
-6.6.1
+6.7

buildSrc/src/testFixtures/java/org/elasticsearch/gradle/test/GradleThreadsFilter.java

@@ -30,6 +30,9 @@ public class GradleThreadsFilter implements ThreadFilter {
 
     @Override
     public boolean reject(Thread t) {
-        return t.getName().startsWith("Exec process") || t.getName().startsWith("File watcher consumer");
+        return t.getName().startsWith("Exec process")
+            || t.getName().startsWith("File watcher consumer")
+            || t.getName().startsWith("Memory manager");
+
     }
 }

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.6.1-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.7-all.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionSha256Sum=11657af6356b7587bfb37287b5992e94a9686d5c8a0a1b60b87b9928a2decde5
+distributionSha256Sum=0080de8491f0918e4f529a6db6820fa0b9e818ee2386117f4394f95feb1d5583