Remove auth-options support from initdb

When --auth was added to initdb in commit e7029b2127 it had support
for auth options separated by space from the auth type, like:

    --auth pam <servicename>
    --auth ident sameuser

Passing an option to the ident auth type was removed in 01c1a12a5b
which left the pam auth-options support in place. 8a02339e9b broke
this by inverting a calculation in the strncmp arguments, which went
unnoticed for a long time.  The ability to pass options to the auth
type was never documented.

Rather than fixing the support for an undocumented feature which has
been broken for all supported versions, and which only supports one
out of many auth types which can take options, it is removed.

Reported-by: Jingxian Li <aqktjcm@qq.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Aleksander Alekseev <aleksander@timescale.com>
Discussion: https://postgr.es/m/tencent_29731C7C7E6A2F9FB807C3A1DC3D81293C06@qq.com

src/bin/initdb/initdb.c

@@ -102,7 +102,7 @@ static const char *const auth_methods_host[] = {
 	"sspi",
 #endif
 #ifdef USE_PAM
-	"pam", "pam ",
+	"pam",
 #endif
 #ifdef USE_BSD_AUTH
 	"bsd",
@@ -118,7 +118,7 @@ static const char *const auth_methods_host[] = {
 static const char *const auth_methods_local[] = {
 	"trust", "reject", "scram-sha-256", "md5", "password", "peer", "radius",
 #ifdef USE_PAM
-	"pam", "pam ",
+	"pam",
 #endif
 #ifdef USE_BSD_AUTH
 	"bsd",
@@ -2512,10 +2512,6 @@ check_authmethod_valid(const char *authmethod, const char *const *valid_methods,
 	{
 		if (strcmp(authmethod, *p) == 0)
 			return;
-		/* with space = param */
-		if (strchr(authmethod, ' '))
-			if (strncmp(authmethod, *p, (authmethod - strchr(authmethod, ' '))) == 0)
-				return;
 	}
 
 	pg_fatal("invalid authentication method \"%s\" for \"%s\" connections",