[Wasm] Remove bootstrapping code that accidentally broke exceptions in VMs without JSTag

Update the JSTag absence simulation to cover this case in tests.

#KT-81372 Fixed

Author: bashor

compiler/ir/backend.wasm/src/org/jetbrains/kotlin/backend/wasm/wasmCompiler.kt

@@ -349,8 +349,8 @@ $referencesToQualifiedAndImportedDeclarations
         // Save WebAssembly.JSTag into a local variable to work around [a problem in JavaScriptCore](https://bugs.webkit.org/show_bug.cgi?id=297126), 
         // which doesn't allow us to check if JSTag is used as a tag inside a wasm module.
         ""
-    }const wasmJsTag = WebAssembly.JSTag;
-    const wasmTag =${if (useJsTag) " wasmJsTag ??" else "" } new WebAssembly.Tag({ parameters: ['externref'] });
+    }const wasmJsTag = ${if (useJsTag) "WebAssembly.JSTag" else "void 0"};
+    const wasmTag = wasmJsTag ?? new WebAssembly.Tag({ parameters: ['externref'] });
 
     const js_code = {
 $jsCodeBodyIndented

compiler/testData/codegen/box/size/add.kt

@@ -2,7 +2,7 @@
 
 // RUN_THIRD_PARTY_OPTIMIZER
 // WASM_DCE_EXPECTED_OUTPUT_SIZE: wasm  52_517
-// WASM_DCE_EXPECTED_OUTPUT_SIZE: mjs    6_197
+// WASM_DCE_EXPECTED_OUTPUT_SIZE: mjs    6_130
 // WASM_OPT_EXPECTED_OUTPUT_SIZE:           76
 
 // FILE: test.kt

compiler/testData/codegen/box/size/helloWorld.kt

@@ -2,7 +2,7 @@
 
 // RUN_THIRD_PARTY_OPTIMIZER
 // WASM_DCE_EXPECTED_OUTPUT_SIZE: wasm  52_821
-// WASM_DCE_EXPECTED_OUTPUT_SIZE: mjs    6_132
+// WASM_DCE_EXPECTED_OUTPUT_SIZE: mjs    6_065
 // WASM_OPT_EXPECTED_OUTPUT_SIZE:        3_911
 
 // IGNORE_BACKEND: WASM_WASI

compiler/testData/codegen/box/size/helloWorldPromise.kt

@@ -2,7 +2,7 @@
 
 // RUN_THIRD_PARTY_OPTIMIZER
 // WASM_DCE_EXPECTED_OUTPUT_SIZE: wasm 52_924
-// WASM_DCE_EXPECTED_OUTPUT_SIZE:  mjs  6_368
+// WASM_DCE_EXPECTED_OUTPUT_SIZE:  mjs  6_301
 // WASM_OPT_EXPECTED_OUTPUT_SIZE:       4_131
 
 // FILE: test.kt

compiler/testData/codegen/box/size/objectsOptimization.kt

@@ -2,7 +2,7 @@
 
 // RUN_THIRD_PARTY_OPTIMIZER
 // WASM_DCE_EXPECTED_OUTPUT_SIZE: wasm 57_045
-// WASM_DCE_EXPECTED_OUTPUT_SIZE:  mjs  6_063
+// WASM_DCE_EXPECTED_OUTPUT_SIZE:  mjs  5_996
 // WASM_OPT_EXPECTED_OUTPUT_SIZE:       4_822
 
 // IGNORE_BACKEND: WASM_WASI

compiler/testData/codegen/box/size/ok.kt

@@ -2,7 +2,7 @@
 
 // RUN_THIRD_PARTY_OPTIMIZER
 // WASM_DCE_EXPECTED_OUTPUT_SIZE: wasm 52_568
-// WASM_DCE_EXPECTED_OUTPUT_SIZE:  mjs  6_063
+// WASM_DCE_EXPECTED_OUTPUT_SIZE:  mjs  5_996
 // WASM_OPT_EXPECTED_OUTPUT_SIZE:       3_849
 
 // IGNORE_BACKEND: WASM_WASI

compiler/testData/codegen/box/size/removeUnusedOverride.kt

@@ -3,7 +3,7 @@
 
 // RUN_THIRD_PARTY_OPTIMIZER
 // WASM_DCE_EXPECTED_OUTPUT_SIZE: wasm  53_274
-// WASM_DCE_EXPECTED_OUTPUT_SIZE: mjs    6_063
+// WASM_DCE_EXPECTED_OUTPUT_SIZE: mjs    5_996
 // WASM_OPT_EXPECTED_OUTPUT_SIZE:        3_875
 
 // IGNORE_BACKEND: WASM_WASI

libraries/stdlib/wasm/js/internal/ExceptionHelpers.kt

@@ -17,8 +17,7 @@ internal fun throwValue(t: Throwable): Nothing {
 // If WebAssembly.JSTag is going to be used for wasm exceptions, use a helper function throwing an exception from JS.
 // It's required to work around [an issue in JavaScriptCore](https://bugs.webkit.org/show_bug.cgi?id=297134)
 // Otherwise, an empty function is provided, and exceptions will be thrown from wasm code.
-// TODO remove 'typeof wasmJsTag === 'undefined' || ' after bootstrap 
-@JsFun("typeof wasmJsTag === 'undefined' || wasmTag === wasmJsTag ? (e) => { throw e; } : () => {}")
+@JsFun("wasmTag === wasmJsTag ? (e) => { throw e; } : () => {}")
 internal external fun jsThrow(e: JsAny?)
 
 @ExcludedFromCodegen