bpo-34523: Use _PyCoreConfig instead of globals (GH-9005)

Use the core configuration of the interpreter, rather
than using global configuration variables. For example, replace
Py_QuietFlag with core_config->quiet.
diff --git a/Modules/main.c b/Modules/main.c
index bf7290a..1ab555b 100644
--- a/Modules/main.c
+++ b/Modules/main.c
@@ -951,18 +951,18 @@
 
 
 static void
-pymain_header(_PyMain *pymain)
+pymain_header(_PyMain *pymain, const _PyCoreConfig *config)
 {
-    if (Py_QuietFlag) {
+    if (config->quiet) {
         return;
     }
 
-    if (!Py_VerboseFlag && (RUN_CODE(pymain) || !pymain->stdin_is_interactive)) {
+    if (!config->verbose && (RUN_CODE(pymain) || !pymain->stdin_is_interactive)) {
         return;
     }
 
     fprintf(stderr, "Python %s on %s\n", Py_GetVersion(), Py_GetPlatform());
-    if (!Py_NoSiteFlag) {
+    if (config->site_import) {
         fprintf(stderr, "%s\n", COPYRIGHT);
     }
 }
@@ -1041,12 +1041,12 @@
 
 
 static void
-pymain_import_readline(_PyMain *pymain)
+pymain_import_readline(_PyMain *pymain, const _PyCoreConfig *config)
 {
-    if (Py_IsolatedFlag) {
+    if (config->isolated) {
         return;
     }
-    if (!Py_InspectFlag && RUN_CODE(pymain)) {
+    if (!config->inspect && RUN_CODE(pymain)) {
         return;
     }
     if (!isatty(fileno(stdin))) {
@@ -1591,8 +1591,8 @@
 
     PyCompilerFlags cf = {.cf_flags = 0};
 
-    pymain_header(pymain);
-    pymain_import_readline(pymain);
+    pymain_header(pymain, config);
+    pymain_import_readline(pymain, config);
 
     if (pymain->command) {
         pymain->status = pymain_run_command(pymain->command, &cf);