Introduce KClass-based cache for KPackageFragment

* It is a heavy-weight object that is hard to compute
* It is being constructed each type _cached_ method ref is used in equals/hashCode
* Module name is deliberately ignored, corresponding doc is added where appropriate 

#KT-48136

Merge-request: KT-MR-6817
Merged-by: Vsevolod Tolstopyatov <qwwdfsad@gmail.com>

compiler/testData/codegen/box/reflection/jvmKPackageCaching.kt

@@ -0,0 +1,13 @@
+// TARGET_BACKEND: JVM_IR
+// FULL_JDK
+// WITH_REFLECT
+import kotlin.jvm.internal.*
+
+class A
+fun box(): String {
+    val pckg = Reflection.getOrCreateKotlinPackage(A::class.java)
+    System.gc()
+    val pckg2 = Reflection.getOrCreateKotlinPackage(A::class.java)
+    if (pckg === pckg2) return "OK"
+    return "Fail"
+}

compiler/testData/codegen/box/reflection/jvmKTypeCaching.kt

@@ -0,0 +1,13 @@
+// TARGET_BACKEND: JVM_IR
+// FULL_JDK
+// WITH_REFLECT
+
+class A
+
+fun box(): String {
+    val clz = A::class
+    System.gc()
+    val clz2 = A::class
+    if (clz === clz2) return "OK"
+    return "Fail"
+}