find redeclare in mulit files.

RedeclareInspection can find redeclare in multiple files.

some tests failed, and it seems not related to RedeclareInspection.I will see whether it works on ci.
```
junit.framework.AssertionFailedError: /xxx/xxx/work/go-lang-idea-plugin/testdata/psi/resolve/calls/ConversionToLocallyImportedType/test/test.go (No such file or directory)
	at ro.redeul.google.go.GoFileBasedPsiTestCase.parseFile(GoFileBasedPsiTestCase.java:167)
	at ro.redeul.google.go.GoFileBasedPsiTestCase$4.process(GoFileBasedPsiTestCase.java:132)
	at ro.redeul.google.go.GoFileBasedPsiTestCase$4.process(GoFileBasedPsiTestCase.java:129)
	at com.intellij.util.FilteringProcessor.process(FilteringProcessor.java:35)
	at com.intellij.openapi.vfs.VfsUtilCore.processFilesRecursively(VfsUtilCore.java:552)
	at ro.redeul.google.go.GoFileBasedPsiTestCase.doDirectoryTest(GoFileBasedPsiTestCase.java:119)
	at ro.redeul.google.go.GoFileBasedPsiTestCase.doTest(GoFileBasedPsiTestCase.java:59)
	at ro.redeul.google.go.resolve.GoResolveCallsTest.testConversionToLocallyImportedType(GoResolveCallsTest.java:85)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at com.intellij.testFramework.UsefulTestCase.access$001(UsefulTestCase.java:84)
	at com.intellij.testFramework.UsefulTestCase$2.run(UsefulTestCase.java:301)
	at com.intellij.openapi.application.impl.ApplicationImpl.runWriteAction(ApplicationImpl.java:938)
	at com.intellij.testFramework.PlatformTestCase$6.run(PlatformTestCase.java:713)
	at com.intellij.testFramework.PlatformTestCase.invokeTestRunnable(PlatformTestCase.java:729)
	at com.intellij.testFramework.UsefulTestCase.runTest(UsefulTestCase.java:317)
	at com.intellij.testFramework.PlatformTestCase$5.run(PlatformTestCase.java:639)
	at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:199)
	at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:715)
	at java.awt.EventQueue.access$400(EventQueue.java:82)
	at java.awt.EventQueue$2.run(EventQueue.java:676)
	at java.awt.EventQueue$2.run(EventQueue.java:674)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:86)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:685)
	at com.intellij.ide.IdeEventQueue.defaultDispatchEvent(IdeEventQueue.java:746)
	at com.intellij.ide.IdeEventQueue._dispatchEvent(IdeEventQueue.java:576)
	at com.intellij.ide.IdeEventQueue.dispatchEvent(IdeEventQueue.java:383)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:296)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:211)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:201)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:196)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:188)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
```
I just update my java to 8