LibJS: Replace strings with the search value coerced to a string

This only causes 1 new test262 test to pass. Other tests that rely on
this coercion fail due to receiving an unexpected value for 'this' when
invoking a functional replacement. For example:

    String/prototype/replaceAll/replaceValue-call-matching-empty.js

Receives 'undefined' for 'this' in the functional replacement invocation
but is expected to receive the global 'this'.

Userland/Libraries/LibJS/Tests/builtins/String/String.prototype.replace.js

@@ -176,3 +176,24 @@ test("replacement value is evaluated before searching the source string", () =>
     expect(newString).toBe("");
     expect(calls).toBe(2);
 });
+
+test("search value is coerced to a string", () => {
+    var calls = 0;
+    var coerced;
+
+    var searchValue = {
+        toString: function () {
+            calls += 1;
+            return "x";
+        },
+    };
+
+    var replaceValue = function (matched) {
+        coerced = matched;
+        return "abc";
+    };
+
+    var newString = "x".replace(searchValue, replaceValue);
+    expect(newString).toBe("abc");
+    expect(coerced).toBe("x");
+});

Userland/Libraries/LibJS/Tests/builtins/String/String.prototype.replaceAll.js

@@ -122,3 +122,24 @@ test("replacement value is evaluated before searching the source string", () =>
     expect(newString).toBe("");
     expect(calls).toBe(2);
 });
+
+test("search value is coerced to a string", () => {
+    var calls = 0;
+    var coerced;
+
+    var searchValue = {
+        toString: function () {
+            calls += 1;
+            return "x";
+        },
+    };
+
+    var replaceValue = function (matched) {
+        coerced = matched;
+        return "abc";
+    };
+
+    var newString = "x".replaceAll(searchValue, replaceValue);
+    expect(newString).toBe("abc");
+    expect(coerced).toBe("x");
+});