SONAR-7678 server-side stateless settings

* Settings class becomes abstract as multiple implementations
are used. Can't become an interface for binary
backward-compatibility of API

* tests should use MapSettings, an in-memory implementation
of Settings

* web server uses a thread-specific cache of settings when
processing HTTP requests

* web server does not have a cache of settings during startup,
except for the system settings loaded from sonar.properties

* Compute Engine uses a thread-specific cache of settings when
  processing a task. Cache is clear at end of task.

 * some useless methods of PersistentSettings are removed

1 files changed, 2 insertions, 1 deletions

diff --git a/plugins/sonar-xoo-plugin/src/test/java/org/sonar/xoo/lang/XooTokenizerTest.java b/plugins/sonar-xoo-plugin/src/test/java/org/sonar/xoo/lang/XooTokenizerTest.java
index aaae76aa475..a5741a255f0 100644
--- a/plugins/sonar-xoo-plugin/src/test/java/org/sonar/xoo/lang/XooTokenizerTest.java
+++ b/plugins/sonar-xoo-plugin/src/test/java/org/sonar/xoo/lang/XooTokenizerTest.java
@@ -34,6 +34,7 @@ import org.sonar.api.config.Settings;
 
 import java.io.File;
 import java.io.IOException;
+import org.sonar.api.config.MapSettings;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.mockito.Mockito.mock;
@@ -54,7 +55,7 @@ public class XooTokenizerTest {
     baseDir = temp.newFolder();
     fileSystem = new DefaultFileSystem(baseDir.toPath());
     when(context.fileSystem()).thenReturn(fileSystem);
-    settings = new Settings();
+    settings = new MapSettings();
     when(context.settings()).thenReturn(settings);
   }