[FIR] Sort KtSourceFiles analogously to KtFiles

The
`IncrementalJsFirKlibCompilerWithScopeExpansionRunnerTestGenerate
.testSerializedSubClassAndChangedInterfaces`
test fail because the checksums of
the `manifest` files don't match
after the full recompilation.
It happens, because the `b.kt` file may be passed
to the compiler before `a.kt`, in which case while
generating the data class members the compiler
will generate a call to `Any::hashCode` when
accessing the hashcode of the `a` property instead
of generating a call to the fake override
`A::hashCode`.
When working with PSI, the compiler sorts the
input files to at `KotlinCoreEnvironment.kt:200`.

This change removes the flaky
behavior by sorting the input files.

compiler/cli/src/org/jetbrains/kotlin/cli/common/GroupedKtSources.kt

@@ -17,6 +17,7 @@ import org.jetbrains.kotlin.cli.jvm.compiler.forAllFiles
 import org.jetbrains.kotlin.config.CommonConfigurationKeys
 import org.jetbrains.kotlin.config.CompilerConfiguration
 import org.jetbrains.kotlin.idea.KotlinFileType
+import java.util.TreeSet
 
 private const val kotlinFileExtensionWithDot = ".${KotlinFileType.EXTENSION}"
 private const val javaFileExtensionWithDot = ".${JavaFileType.DEFAULT_EXTENSION}"
@@ -35,13 +36,19 @@ fun collectSources(
     return collectSources(compilerConfiguration, projectEnvironment.project, messageCollector)
 }
 
+private val ktSourceFileComparator = Comparator<KtSourceFile> { o1, o2 ->
+    val path1 = o1.path ?: error("Expected a file with a well-defined path")
+    val path2 = o2.path ?: error("Expected a file with a well-defined path")
+    path1.compareTo(path2)
+}
+
 fun collectSources(
     compilerConfiguration: CompilerConfiguration,
     project: Project,
     messageCollector: MessageCollector
 ): GroupedKtSources {
-    val platformSources = linkedSetOf<KtSourceFile>()
-    val commonSources = linkedSetOf<KtSourceFile>()
+    val platformSources = TreeSet(ktSourceFileComparator)
+    val commonSources = TreeSet(ktSourceFileComparator)
     val sourcesByModuleName = mutableMapOf<String, MutableSet<KtSourceFile>>()
 
     // TODO: the scripts checking should be part of the scripting plugin functionality, as it is implemented now in ScriptingProcessSourcesBeforeCompilingExtension