Remove basic_string<unsigned_char> from embind

Only `char`, `wchar`, `char8`, `char16`, and `char32` are valid
specialization for `std::basic_string`:
https://en.cppreference.com/w/cpp/string/basic_string

But libc++ had a base template for `basic_string` that allowed any type
to be passed for a long time. It looks there have been several attempts
to remove this after which they restored it due to complaints, in
chronological order:
llvm/llvm-project@aeecef0
llvm/llvm-project@08a0faf
llvm/llvm-project@e30a148
llvm/llvm-project#66153
llvm/llvm-project#72694

The last one, llvm/llvm-project#72694,
eventually removed it. So `std::basic_string<unsigned_char>` is not
allowed anymore. This removes all uses of
`std::basic_string<unsigned_char>` from embind.

This needs to be done to update libc++ to LLVM 19 (emscripten-core#22994). I'm
uploading this as a separate PR because this removes a functionality
from embind.

Author: aheejin

system/lib/embind/bind.cpp

@@ -149,8 +149,6 @@ EMSCRIPTEN_BINDINGS(builtin) {
   register_float<double>("double");
 
   _embind_register_std_string(TypeID<std::string>::get(), "std::string");
-  _embind_register_std_string(
-    TypeID<std::basic_string<unsigned char>>::get(), "std::basic_string<unsigned char>");
   _embind_register_std_wstring(TypeID<std::wstring>::get(), sizeof(wchar_t), "std::wstring");
   _embind_register_std_wstring(TypeID<std::u16string>::get(), sizeof(char16_t), "std::u16string");
   _embind_register_std_wstring(TypeID<std::u32string>::get(), sizeof(char32_t), "std::u32string");

test/embind/embind.test.js

@@ -449,33 +449,6 @@ module({
             assert.equal('ABCD', e);
         });
 
-        test("can pass Uint8Array to std::basic_string<unsigned char>", function() {
-            var e = cm.emval_test_take_and_return_std_basic_string_unsigned_char(new Uint8Array([65, 66, 67, 68]));
-            assert.equal('ABCD', e);
-        });
-
-        test("can pass long string to std::basic_string<unsigned char>", function() {
-            var s = 'this string is long enough to exceed the short string optimization';
-            var e = cm.emval_test_take_and_return_std_basic_string_unsigned_char(s);
-            assert.equal(s, e);
-        });
-
-        test("can pass Uint8ClampedArray to std::basic_string<unsigned char>", function() {
-            var e = cm.emval_test_take_and_return_std_basic_string_unsigned_char(new Uint8ClampedArray([65, 66, 67, 68]));
-            assert.equal('ABCD', e);
-        });
-
-
-        test("can pass Int8Array to std::basic_string<unsigned char>", function() {
-            var e = cm.emval_test_take_and_return_std_basic_string_unsigned_char(new Int8Array([65, 66, 67, 68]));
-            assert.equal('ABCD', e);
-        });
-
-        test("can pass ArrayBuffer to std::basic_string<unsigned char>", function() {
-            var e = cm.emval_test_take_and_return_std_basic_string_unsigned_char((new Int8Array([65, 66, 67, 68])).buffer);
-            assert.equal('ABCD', e);
-        });
-
         test("can pass string to std::string", function() {
             var string = stdStringIsUTF8?"aeiáéíαειЖЛФ從獅子€":"ABCD";
 

test/embind/embind_test.cpp

@@ -246,10 +246,6 @@ std::string emval_test_take_and_return_std_string_const_ref(const std::string& s
   return str;
 }
 
-std::basic_string<unsigned char> emval_test_take_and_return_std_basic_string_unsigned_char(std::basic_string<unsigned char> str) {
-  return str;
-}
-
 std::wstring take_and_return_std_wstring(std::wstring str) {
   return str;
 }
@@ -1914,7 +1910,6 @@ EMSCRIPTEN_BINDINGS(tests) {
   //function("emval_test_take_and_return_const_char_star", &emval_test_take_and_return_const_char_star);
   function("emval_test_take_and_return_std_string", &emval_test_take_and_return_std_string);
   function("emval_test_take_and_return_std_string_const_ref", &emval_test_take_and_return_std_string_const_ref);
-  function("emval_test_take_and_return_std_basic_string_unsigned_char", &emval_test_take_and_return_std_basic_string_unsigned_char);
   function("take_and_return_std_wstring", &take_and_return_std_wstring);
   function("take_and_return_std_u16string", &take_and_return_std_u16string);
   function("take_and_return_std_u32string", &take_and_return_std_u32string);