Make inner classes static where possible in tycho-core

Using JDT UI "Make inner classes static where possible" clean-up on
Tycho core

tycho-core/src/main/java/org/eclipse/tycho/core/osgitools/DependencyComputer.java

@@ -126,7 +126,7 @@ public String toString() {
         }
     }
 
-    private final class VisiblePackages {
+    private static final class VisiblePackages {
         private final Map<BundleRevision, Set<AccessRule>> visiblePackages = new HashMap<>();
         private final BundleRevision consumerHost;
 

tycho-core/src/main/java/org/eclipse/tycho/p2/repository/AbstractArtifactRepository2.java

@@ -233,7 +233,7 @@ public final OutputStream getOutputStream(IArtifactDescriptor descriptor) throws
         }
     }
 
-    private class CommittingArtifactOutputStream extends OutputStream implements IStateful {
+    private static class CommittingArtifactOutputStream extends OutputStream implements IStateful {
         final IArtifactSink artifactSink;
         final OutputStream artifactOutputStream;
 

tycho-core/src/main/java/org/eclipse/tycho/p2tools/MirrorApplicationServiceImpl.java

@@ -359,7 +359,7 @@ public void close() {
 
     }
 
-    private final class MappingRule {
+    private static final class MappingRule {
         public final String filter;
         public final String urlPattern;
 

tycho-core/src/test/java/org/eclipse/tycho/test/util/LogVerifier.java

@@ -38,7 +38,7 @@ public class LogVerifier extends Verifier {
 
     private static boolean WRITE_TO_CONSOLE = false;
 
-    private class MemoryLog implements Logger {
+    private static class MemoryLog implements Logger {
 
         final StringBuilder errors = new StringBuilder();
         final StringBuilder warnings = new StringBuilder();