[kotlin.reflect] Introduce ClassValue-based cache for KClassImpl

* Replace pcollections with ClassValue/ConcurrentHashMap-based caches
* Do not store weak references, instead cache strong references and count on ClassValue to unload the corresponding classloader if necessary
* ConcurrentHashMap does not rely on WeakReference as it's only selected on Android where classloader leaks don't exist
* Update reflect/scripting JDK requirement to Java 8 in order to proceed

#KT-53454
#KT-50705


Merge-request: KT-MR-6788
Merged-by: Vsevolod Tolstopyatov <qwwdfsad@gmail.com>

native/native.tests/tests-gen/org/jetbrains/kotlin/konan/blackboxtest/NativeCodegenBoxTestGenerated.java

@@ -15440,18 +15440,6 @@ public class NativeCodegenBoxTestGenerated extends AbstractNativeCodegenBoxTest
             }
         }
 
-        @Nested
-        @TestMetadata("compiler/testData/codegen/box/hashPMap")
-        @TestDataPath("$PROJECT_ROOT")
-        @Tag("codegen")
-        @UseExtTestCaseGroupProvider()
-        public class HashPMap {
-            @Test
-            public void testAllFilesPresentInHashPMap() throws Exception {
-                KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/codegen/box/hashPMap"), Pattern.compile("^(.+)\\.kt$"), null, TargetBackend.NATIVE, true);
-            }
-        }
-
         @Nested
         @TestMetadata("compiler/testData/codegen/box/ieee754")
         @TestDataPath("$PROJECT_ROOT")