Change test storage from List to class in Fix plugin

What's done:
* Change test storage from List to class in plugin
Closes #221

save-plugins/fix-and-warn-plugin/src/commonMain/kotlin/org/cqfn/save/plugins/fixandwarn/FixAndWarnPlugin.kt

@@ -67,7 +67,7 @@ class FixAndWarnPlugin(
     override fun handleFiles(files: Sequence<TestFiles>): Sequence<TestResult> {
         // Need to update private fields after validation
         initOrUpdateConfigs()
-        val expectedFiles = files.map { it as FixPlugin.FixTestFiles }.map { it.expected }
+        val expectedFiles = files.map { it as FixPlugin.Test }.map { it.expected }
 
         // Remove (in place) warnings from test files before fix plugin execution
         val filesAndTheirWarningsMap = removeWarningsFromExpectedFiles(expectedFiles)

save-plugins/fix-plugin/src/commonMain/kotlin/org/cqfn/save/plugins/fix/FixPlugin.kt

@@ -50,7 +50,7 @@ class FixPlugin(
         val fixPluginConfig = testConfig.pluginConfigs.filterIsInstance<FixPluginConfig>().single()
         val generalConfig = testConfig.pluginConfigs.filterIsInstance<GeneralConfig>().single()
 
-        return files.map { it as FixTestFiles }.chunked(fixPluginConfig.batchSize!!.toInt()).map { chunk ->
+        return files.map { it as Test }.chunked(fixPluginConfig.batchSize!!.toInt()).map { chunk ->
             val pathMap = chunk.map { it.expected to it.test }
             val pathCopyMap = pathMap.map { (expected, test) -> expected to createTestFile(test, generalConfig) }
             val testCopyNames =
@@ -172,19 +172,9 @@ class FixPlugin(
         .toList()
         .joinToString { (type, lines) -> "$type: $lines lines" }
 
-    /**
-     * @property expected expected file
-     */
-    interface FixTestFiles : TestFiles {
-        /**
-         * path to expected file
-         */
-        val expected: Path
-    }
-
     /**
      * @property test test file
      * @property expected expected file
      */
-    class Test(override val test: Path, override val expected: Path) : FixTestFiles
+    class Test(override val test: Path, val expected: Path) : TestFiles
 }

save-plugins/fix-plugin/src/commonNonJsTest/kotlin/org/cqfn/save/plugins/fix/FixPluginTest.kt

@@ -171,7 +171,7 @@ class FixPluginTest {
         useInternalRedirections = false
     )
         .discoverTestFiles(tmpDir)
-        .map { it as FixPlugin.FixTestFiles }
+        .map { it as FixPlugin.Test }
         .map { it.expected to it.test }
         .toList()
 }