Implement hack to support both remove() and removeAt() in MutableList<Int>

Also add couple of tests about CharSequence.get

compiler/testData/codegen/bytecodeText/builtinFunctions/charSequence.kt

@@ -0,0 +1,7 @@
+abstract class A1 : CharSequence {}
+
+abstract class A2 : CharSequence {
+    override fun get(index: Int) = 'z';
+}
+
+// 2 public final bridge charAt

compiler/testData/codegen/bytecodeText/builtinFunctions/removeAt.kt

@@ -0,0 +1,116 @@
+abstract class A1<T> : MutableList<T> {
+    override fun remove(x: T): Boolean = true
+    override fun removeAt(index: Int): T = null!!
+}
+
+abstract class A2 : MutableList<String> {
+    override fun remove(x: String): Boolean = true
+    override fun removeAt(index: Int): String = null!!
+}
+
+abstract class A3 : java.util.AbstractList<String>() {
+    override fun remove(x: String): Boolean = true
+    override fun removeAt(index: Int): String = null!!
+}
+
+abstract class A4 : java.util.AbstractList<String>() {
+    override abstract fun remove(x: String): Boolean
+    override abstract fun removeAt(index: Int): String
+}
+
+abstract class A5 : java.util.ArrayList<String>() {
+    override fun remove(x: String): Boolean = true
+    override fun removeAt(index: Int): String = null!!
+}
+
+abstract class A6 : java.util.ArrayList<String>() {
+    override abstract fun remove(x: String): Boolean
+    override abstract fun removeAt(index: Int): String
+}
+
+abstract class A7 : MutableList<String>
+abstract class A8 : java.util.ArrayList<String>()
+
+interface A9 : MutableList<String> {}
+
+abstract class A10 : MutableList<Int> {
+    override fun remove(x: Int): Boolean = true
+    override fun removeAt(index: Int): Int = 1
+}
+
+fun box(
+        a1: A1<String>,
+        a2: A2,
+        a3: A3,
+        a4: A4,
+        a5: A5,
+        a6: A6,
+        a7: A7,
+        a8: A8,
+        a9: A9,
+        a10: A10,
+        c1: MutableList<String>,
+        c2: MutableList<Int>
+) {
+    a1.removeAt(1)
+    a1.remove("")
+
+    a2.removeAt(1)
+    a2.remove("")
+
+    a3.removeAt(1)
+    a3.remove("")
+
+    a4.removeAt(1)
+    a4.remove("")
+
+    a5.removeAt(1)
+    a5.remove("")
+
+    a6.removeAt(1)
+    a6.remove("")
+
+    a7.removeAt(1)
+    a7.remove("")
+
+    a8.removeAt(1)
+    a8.remove("")
+
+    a9.removeAt(1)
+    a9.remove("")
+
+    a10.removeAt(1)
+    a10.remove(2)
+
+    c1.removeAt(1)
+    c1.remove("")
+
+    c2.removeAt(1)
+    c2.remove(2)
+}
+
+/*
+9 public final bridge remove\(I\)  -> Bridges for removeAt from A2-A10
+7 public synthetic bridge remove\(I\)Ljava/lang/Object; -> Synthetic bridges from A2-A9
+16 INVOKEVIRTUAL A[0-9]+.removeAt \(I\) -> calls in bridges
+1 public remove\(Ljava/lang/Integer;\)Z -> implementation in A10
+3 public abstract removeAt\(I\) -> A4, A6, A7
+1 INVOKEINTERFACE A9\.remove \(I\) -> call A9.removeAt
+1 INVOKEINTERFACE A9\.remove \(Ljava/lang/Object;\) -> call A9.remove
+9 INVOKEVIRTUAL A[0-9]+\.remove \(I\) -> calls to A1-A9.removeAt
+*/
+
+// 9 public final bridge remove\(I\)
+// 7 public synthetic bridge remove\(I\)Ljava/lang/Object;
+// 1 public remove\(Ljava/lang/Integer;\)Z
+// 3 public abstract removeAt\(I\)
+// 16 INVOKEVIRTUAL A[0-9]+.removeAt \(I\)
+// 1 INVOKEINTERFACE A9\.remove \(I\)
+// 1 INVOKEINTERFACE A9\.remove \(Ljava/lang/Object;\)
+// 9 INVOKEVIRTUAL A[0-9]+\.remove \(I\)
+// 1 INVOKEVIRTUAL A10\.remove \(I\)
+// 9 INVOKEVIRTUAL A[0-9]+\.remove \(I\)
+// 1 INVOKEVIRTUAL A10\.remove \(I\)
+// 2 INVOKEINTERFACE java\/util\/List.remove \(I\)
+// 2 INVOKEINTERFACE java\/util\/List.remove \(Ljava/lang/Object;\)
+