bpo-32030: Add _PyCoreConfig.warnoptions (#4936)

Merge _PyCoreConfig_ReadEnv() into _PyCoreConfig_Read(), and
_Py_CommandLineDetails usage is now restricted to pymain_cmdline().

Changes:

* _PyCoreConfig: Add nxoption, xoptions, nwarnoption and warnoptions
* Add _PyCoreConfig.program: argv[0] or ""
* Move filename, command, module and xoptions from
  _Py_CommandLineDetails to _PyMain. xoptions _Py_OptList becomes
  (int, wchar_t**) list.
* Add pymain_cmdline() function
* Rename copy_argv() to copy_wstrlist(). Rename clear_argv() to
  clear_wstrlist(). Remove _Py_OptList structure: use (int,
  wchar_t**) list instead.
* Rename pymain_set_flag_from_env() to pymain_get_env_flag()
* Rename pymain_set_flags_from_env() to pymain_get_env_flags()
* _PyMainInterpreterConfig_Read() now creates the warnoptions from
  _PyCoreConfig.warnoptions
* Inline pymain_add_warning_dev_mode() and
  pymain_add_warning_bytes_flag() into config_init_warnoptions()
* Inline pymain_get_program_name() into _PyCoreConfig_Read()
* _Py_CommandLineDetails: Replace warning_options with nwarnoption
  and warnoptions. Replace env_warning_options with nenv_warnoption
  and env_warnoptions.
* pymain_warnings_envvar() now has a single implementation for
  Windows and Unix: use config_get_env_var_dup() to also get the
  variable as wchar_t* on Unix.

Author: vstinner

Include/pylifecycle.h

@@ -54,7 +54,6 @@ PyAPI_FUNC(int) Py_SetStandardStreamEncoding(const char *encoding,
 PyAPI_FUNC(_PyInitError) _Py_InitializeCore(const _PyCoreConfig *);
 PyAPI_FUNC(int) _Py_IsCoreInitialized(void);
 
-PyAPI_FUNC(_PyInitError) _PyCoreConfig_ReadEnv(_PyCoreConfig *);
 PyAPI_FUNC(_PyInitError) _PyCoreConfig_Read(_PyCoreConfig *);
 PyAPI_FUNC(void) _PyCoreConfig_Clear(_PyCoreConfig *);
 PyAPI_FUNC(int) _PyCoreConfig_Copy(

Include/pystate.h

@@ -50,7 +50,14 @@ typedef struct {
 
     int argc;               /* Number of command line arguments,
                                -1 means unset */
-    wchar_t **argv;         /* sys.argv, ignored if argc is negative */
+    wchar_t **argv;         /* Command line arguments */
+    wchar_t *program;       /* argv[0] or "" */
+
+    int nxoption;           /* Number of -X options */
+    wchar_t **xoptions;     /* -X options */
+
+    int nwarnoption;        /* Number of warnings options */
+    wchar_t **warnoptions;  /* Warnings options */
 } _PyCoreConfig;
 
 #define _PyCoreConfig_INIT \