Stabilize unsigned types KT-45653

Deprecate specialized unsigned iterators for removal.

Fix compiler tests:
- drop unsignedLiteralsOn1_2 because apiVersion 1.2 is no longer supported
- drop experimental unsigned literals diagnostic test

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendDiagnosticsTestGenerated.java

@@ -29635,12 +29635,6 @@ public class FirOldFrontendDiagnosticsTestGenerated extends AbstractFirDiagnosti
                 runTest("compiler/testData/diagnostics/tests/unsignedTypes/unsignedLiteralsInsideConstVals.kt");
             }
 
-            @Test
-            @TestMetadata("unsignedLiteralsOn1_2.kt")
-            public void testUnsignedLiteralsOn1_2() throws Exception {
-                runTest("compiler/testData/diagnostics/tests/unsignedTypes/unsignedLiteralsOn1_2.kt");
-            }
-
             @Test
             @TestMetadata("unsignedLiteralsOverflowSignedBorder.kt")
             public void testUnsignedLiteralsOverflowSignedBorder() throws Exception {
@@ -33657,12 +33651,6 @@ public class FirOldFrontendDiagnosticsTestGenerated extends AbstractFirDiagnosti
                 runTest("compiler/testData/diagnostics/testsWithStdLib/experimental/experimentalOnWholeModule.kt");
             }
 
-            @Test
-            @TestMetadata("experimentalUnsignedLiterals.kt")
-            public void testExperimentalUnsignedLiterals() throws Exception {
-                runTest("compiler/testData/diagnostics/testsWithStdLib/experimental/experimentalUnsignedLiterals.kt");
-            }
-
             @Test
             @TestMetadata("fullFqNameUsage.kt")
             public void testFullFqNameUsage() throws Exception {