Compute constant expression as an inspection; minor improvements

Works for unary operation
Do not suggested if replacement is the same as the original code
Replacement is displayed in the quick-fix name

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/constantExpression/afterUnary.java

@@ -0,0 +1,4 @@
+// "Replace '~2' with constant value '-3'" "true"
+class Test {
+  int x = -3;
+}