udev-rule: rework logging about udev rules

This makes the loggers take the most relevant object, i.e. when
applying udev rules to a device, the loggers take sd_device and
UdevRuleToken object, and when parsing udev rules, they take
UdevRuleLine or UdevRuleFile object.

To achieve that, this drops 'iterators' in UdevRules or friends named
`current_file` or so. Instead of that, each object now has its
parent object, e.g. UdevRuleToken.rule_line that references the
UdevRuleLine object the token belonging to. And each function previously
took UdevRules object now takes the most relevant object, e.g. UdevRuleToken.

Solves the discussion in https://github.com/systemd/systemd/pull/26698#discussion_r1129261193.

src/udev/fuzz-udev-rules.c

@@ -27,11 +27,10 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
         fflush(f);
 
         assert_se(rules = udev_rules_new(RESOLVE_NAME_EARLY));
-        r = udev_rules_parse_file(rules, filename);
+        r = udev_rules_parse_file(rules, filename, NULL);
         log_info_errno(r, "Parsing %s: %m", filename);
-        assert_se(IN_SET(r,
-                         0,       /* OK */
-                         -ENOBUFS /* line length exceeded */));
+        assert_se(r >= 0 ||             /* OK */
+                  r == -ENOBUFS);       /* line length exceeded */
 
         return 0;
 }

src/udev/udev-rules.h

@@ -6,6 +6,7 @@
 #include "time-util.h"
 #include "udev-util.h"
 
+typedef struct UdevRuleFile UdevRuleFile;
 typedef struct UdevRules UdevRules;
 typedef struct UdevEvent UdevEvent;
 
@@ -17,8 +18,8 @@ typedef enum {
         _ESCAPE_TYPE_INVALID = -EINVAL,
 } UdevRuleEscapeType;
 
-int udev_rules_parse_file(UdevRules *rules, const char *filename);
-unsigned udev_check_current_rule_file(UdevRules *rules);
+int udev_rules_parse_file(UdevRules *rules, const char *filename, UdevRuleFile **ret);
+unsigned udev_rule_file_get_issues(UdevRuleFile *rule_file);
 UdevRules* udev_rules_new(ResolveNameTiming resolve_name_timing);
 int udev_rules_load(UdevRules **ret_rules, ResolveNameTiming resolve_name_timing);
 UdevRules *udev_rules_free(UdevRules *rules);

src/udev/udevadm-verify.c

@@ -101,13 +101,16 @@ static int parse_argv(int argc, char *argv[]) {
 }
 
 static int verify_rules_file(UdevRules *rules, const char *fname) {
+        UdevRuleFile *file;
         int r;
 
-        r = udev_rules_parse_file(rules, fname);
+        r = udev_rules_parse_file(rules, fname, &file);
         if (r < 0)
                 return log_error_errno(r, "Failed to parse rules file %s: %m", fname);
+        if (r == 0) /* empty file. */
+                return 0;
 
-        unsigned issues = udev_check_current_rule_file(rules);
+        unsigned issues = udev_rule_file_get_issues(file);
         unsigned mask = (1U << LOG_ERR) | (1U << LOG_WARNING);
         if (issues & mask)
                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL),