[embind] Allow raw pointers for individual arguments and return values.

[brendandahl]

Previously, allow_raw_pointer<arg> mapped to allow_raw_pointers, which allowed pointers for all arguments. This PR implements the checks to verify just the specified argument or return value are allowed pointers.

[juj]

The new tests aren't happy on my CI, but give

======================================================================
FAIL: test_embind_no_raw_pointers_wrong_arg_allow (test_other.other.test_embind_no_raw_pointers_wrong_arg_allow)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\buildbot\win11-x64-64gb-9800x3d\emscripten_win11_x64\build\emscripten\main\test\common.py", line 290, in resulting_test
    return func(self, *args)
  File "C:\buildbot\win11-x64-64gb-9800x3d\emscripten_win11_x64\build\emscripten\main\test\test_other.py", line 3369, in test_embind_no_raw_pointers
    self.assert_fail([EMCC, '-lembind', test_file(filename)], 'Implicitly binding raw pointers is illegal')
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\buildbot\win11-x64-64gb-9800x3d\emscripten_win11_x64\build\emscripten\main\test\common.py", line 1212, in assert_fail
    err = self.expect_fail(cmd, **kwargs)
  File "C:\buildbot\win11-x64-64gb-9800x3d\emscripten_win11_x64\build\emscripten\main\test\common.py", line 1197, in expect_fail
    self.assertNotEqual(proc.returncode, 0, 'subprocess unexpectedly succeeded. stderr:\n' + proc.stderr)
    ~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 0 == 0 : subprocess unexpectedly succeeded. stderr:


======================================================================
FAIL: test_embind_no_raw_pointers_wrong_ret_allow (test_other.other.test_embind_no_raw_pointers_wrong_ret_allow)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\buildbot\win11-x64-64gb-9800x3d\emscripten_win11_x64\build\emscripten\main\test\common.py", line 290, in resulting_test
    return func(self, *args)
  File "C:\buildbot\win11-x64-64gb-9800x3d\emscripten_win11_x64\build\emscripten\main\test\test_other.py", line 3369, in test_embind_no_raw_pointers
    self.assert_fail([EMCC, '-lembind', test_file(filename)], 'Implicitly binding raw pointers is illegal')
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\buildbot\win11-x64-64gb-9800x3d\emscripten_win11_x64\build\emscripten\main\test\common.py", line 1212, in assert_fail
    err = self.expect_fail(cmd, **kwargs)
  File "C:\buildbot\win11-x64-64gb-9800x3d\emscripten_win11_x64\build\emscripten\main\test\common.py", line 1197, in expect_fail
    self.assertNotEqual(proc.returncode, 0, 'subprocess unexpectedly succeeded. stderr:\n' + proc.stderr)
    ~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 0 == 0 : subprocess unexpectedly succeeded. stderr:

http://clbri.com:8010/api/v2/logs/273025/raw_inline

Failure happens only on Windows, not on Linux or macOS.