bpo-34589: Make _PyCoreConfig.coerce_c_locale private (GH-9371)

_PyCoreConfig:

* Rename coerce_c_locale to _coerce_c_locale
* Rename coerce_c_locale_warn to _coerce_c_locale_warn

These fields are now private (name prefixed by "_").
diff --git a/Python/coreconfig.c b/Python/coreconfig.c
index fae32e5..1e03ce3 100644
--- a/Python/coreconfig.c
+++ b/Python/coreconfig.c
@@ -303,8 +303,8 @@
     COPY_ATTR(dump_refs);
     COPY_ATTR(malloc_stats);
 
-    COPY_ATTR(coerce_c_locale);
-    COPY_ATTR(coerce_c_locale_warn);
+    COPY_ATTR(_coerce_c_locale);
+    COPY_ATTR(_coerce_c_locale_warn);
     COPY_ATTR(utf8_mode);
 
     COPY_WSTR_ATTR(pycache_prefix);
@@ -811,16 +811,16 @@
     const char *env = _PyCoreConfig_GetEnv(config, "PYTHONCOERCECLOCALE");
     if (env) {
         if (strcmp(env, "0") == 0) {
-            if (config->coerce_c_locale < 0) {
-                config->coerce_c_locale = 0;
+            if (config->_coerce_c_locale < 0) {
+                config->_coerce_c_locale = 0;
             }
         }
         else if (strcmp(env, "warn") == 0) {
-            config->coerce_c_locale_warn = 1;
+            config->_coerce_c_locale_warn = 1;
         }
         else {
-            if (config->coerce_c_locale < 0) {
-                config->coerce_c_locale = 1;
+            if (config->_coerce_c_locale < 0) {
+                config->_coerce_c_locale = 1;
             }
         }
     }
@@ -967,10 +967,10 @@
 static void
 config_init_locale(_PyCoreConfig *config)
 {
-    if (config->coerce_c_locale < 0) {
+    if (config->_coerce_c_locale < 0) {
         /* The C locale enables the C locale coercion (PEP 538) */
         if (_Py_LegacyLocaleDetected()) {
-            config->coerce_c_locale = 1;
+            config->_coerce_c_locale = 1;
         }
     }
 
@@ -1291,7 +1291,7 @@
         }
     }
 
-    if (config->utf8_mode < 0 || config->coerce_c_locale < 0) {
+    if (config->utf8_mode < 0 || config->_coerce_c_locale < 0) {
         config_init_locale(config);
     }
 
@@ -1321,8 +1321,8 @@
     if (config->tracemalloc < 0) {
         config->tracemalloc = 0;
     }
-    if (config->coerce_c_locale < 0) {
-        config->coerce_c_locale = 0;
+    if (config->_coerce_c_locale < 0) {
+        config->_coerce_c_locale = 0;
     }
     if (config->utf8_mode < 0) {
         config->utf8_mode = 0;
@@ -1343,7 +1343,7 @@
         return err;
     }
 
-    assert(config->coerce_c_locale >= 0);
+    assert(config->_coerce_c_locale >= 0);
     assert(config->use_environment >= 0);
     assert(config->filesystem_encoding != NULL);
     assert(config->filesystem_errors != NULL);
diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index 379e860..b735228 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -301,7 +301,7 @@
 static void
 _emit_stderr_warning_for_legacy_locale(const _PyCoreConfig *core_config)
 {
-    if (core_config->coerce_c_locale_warn && _Py_LegacyLocaleDetected()) {
+    if (core_config->_coerce_c_locale_warn && _Py_LegacyLocaleDetected()) {
         PySys_FormatStderr("%s", _C_LOCALE_WARNING);
     }
 }