src/basic: rename uid-alloc-range.[ch] to uid-classification.[ch]

We had both uid-range.h and uid-alloc-range.h. The latter now contains helpers
like {uid,gid}_is_{system,dynamic,container}(), uid_for_system_journal(), so
the existing name is outdated. I think the uid-range.[ch] should stay separate
because it has a bunch of helpers for parsing and printing of uid ranges. So
let's rename as in $subject to better reflect the contents of the file and make
the two sets of files harder to confuse.

src/basic/uid-classification.h

@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include <stdbool.h>
+#include <sys/types.h>
+
+bool uid_is_system(uid_t uid);
+bool gid_is_system(gid_t gid);
+
+static inline bool uid_is_dynamic(uid_t uid) {
+        return DYNAMIC_UID_MIN <= uid && uid <= DYNAMIC_UID_MAX;
+}
+
+static inline bool gid_is_dynamic(gid_t gid) {
+        return uid_is_dynamic((uid_t) gid);
+}
+
+static inline bool uid_is_container(uid_t uid) {
+        return CONTAINER_UID_BASE_MIN <= uid && uid <= CONTAINER_UID_BASE_MAX;
+}
+
+static inline bool gid_is_container(gid_t gid) {
+        return uid_is_container((uid_t) gid);
+}
+
+typedef struct UGIDAllocationRange {
+        uid_t system_alloc_uid_min;
+        uid_t system_uid_max;
+        gid_t system_alloc_gid_min;
+        gid_t system_gid_max;
+} UGIDAllocationRange;
+
+int read_login_defs(UGIDAllocationRange *ret_defs, const char *path, const char *root);
+const UGIDAllocationRange *acquire_ugid_allocation_range(void);
+
+bool uid_for_system_journal(uid_t uid);