K2/tests: add a similar to containsAndOverload test about charAt / get

Related to KT-64846

compiler/testData/diagnostics/tests/j+k/collectionOverrides/charAtAndOverload.fir.kt

@@ -0,0 +1,26 @@
+// SCOPE_DUMP: KA:get
+
+// FILE: A.java
+abstract public class A implements CharSequence {
+    public final int length() {
+        return 0;
+    }
+
+    public char charAt(int index) {
+        return ' ';
+    }
+
+    public char get(int index) {
+        return 'X';
+    }
+}
+
+// FILE: main.kt
+abstract class KA : A() {
+    override fun get(index: Int) = 'O'
+}
+
+fun foo(a: A, ka: KA) {
+    a.get(0)
+    ka.<!UNRESOLVED_REFERENCE!>get<!>(0)
+}

compiler/testData/diagnostics/tests/j+k/collectionOverrides/charAtAndOverload.fir.overrides.txt

@@ -0,0 +1,6 @@
+KA:
+  [Source]: public open override operator fun get(index: R|kotlin/Int|): R|kotlin/Char| from Use site scope of /KA [id: 0]
+    [Enhancement]: public open operator fun get(index: R|kotlin/Int|): R|kotlin/Char| from Java enhancement scope for /A [id: 1]
+    [Enhancement]: /* hidden due to clash */ public open operator fun get(index: R|kotlin/Int|): R|kotlin/Char| from Java enhancement scope for /A [id: 2]
+      [Library]: public abstract operator fun get(index: R|kotlin/Int|): R|kotlin/Char| from Use site scope of kotlin/CharSequence [id: 3]
+

compiler/testData/diagnostics/tests/j+k/collectionOverrides/charAtAndOverload.kt

@@ -0,0 +1,26 @@
+// SCOPE_DUMP: KA:get
+
+// FILE: A.java
+abstract public class A implements CharSequence {
+    public final int length() {
+        return 0;
+    }
+
+    public char charAt(int index) {
+        return ' ';
+    }
+
+    public char get(int index) {
+        return 'X';
+    }
+}
+
+// FILE: main.kt
+abstract class <!CONFLICTING_JVM_DECLARATIONS!>KA<!> : A() {
+    <!CONFLICTING_JVM_DECLARATIONS!>override fun get(index: Int)<!> = 'O'
+}
+
+fun foo(a: A, ka: KA) {
+    a.get(0)
+    ka.get(0)
+}