core: use uniform style for RateLimit initialization

RateLimit is designed so that we can always initialize only the first two
fields explicitly. All other call sites use a single line for this.

src/basic/ratelimit.h

@@ -12,6 +12,8 @@ typedef struct RateLimit {
         usec_t begin;
 } RateLimit;
 
+#define RATELIMIT_OFF (const RateLimit) { .interval = USEC_INFINITY, .burst = UINT_MAX }
+
 static inline void ratelimit_reset(RateLimit *rl) {
         rl->num = rl->begin = 0;
 }

src/core/manager.c

@@ -927,10 +927,7 @@ int manager_new(RuntimeScope runtime_scope, ManagerTestRunFlags test_run_flags,
                 .first_boot = -1,
                 .test_run_flags = test_run_flags,
 
-                .dump_ratelimit = {
-                        .interval = 10 * USEC_PER_MINUTE,
-                        .burst = 10,
-                },
+                .dump_ratelimit = (const RateLimit) { .interval = 10 * USEC_PER_MINUTE, .burst = 10 },
 
                 .executor_fd = -EBADF,
         };

src/core/path.c

@@ -279,8 +279,7 @@ static void path_init(Unit *u) {
 
         p->directory_mode = 0755;
 
-        p->trigger_limit.interval = USEC_INFINITY;
-        p->trigger_limit.burst = UINT_MAX;
+        p->trigger_limit = RATELIMIT_OFF;
 }
 
 void path_free_specs(Path *p) {

src/core/socket.c

@@ -100,8 +100,7 @@ static void socket_init(Unit *u) {
         s->control_pid = PIDREF_NULL;
         s->control_command_id = _SOCKET_EXEC_COMMAND_INVALID;
 
-        s->trigger_limit.interval = USEC_INFINITY;
-        s->trigger_limit.burst = UINT_MAX;
+        s->trigger_limit = RATELIMIT_OFF;
 
         s->poll_limit_interval = USEC_INFINITY;
         s->poll_limit_burst = UINT_MAX;

src/core/unit.c

@@ -132,15 +132,12 @@ Unit* unit_new(Manager *m, size_t size) {
 
         u->last_section_private = -1;
 
-        u->start_ratelimit = (RateLimit) {
+        u->start_ratelimit = (const RateLimit) {
                 m->defaults.start_limit_interval,
-                m->defaults.start_limit_burst
+                m->defaults.start_limit_burst,
         };
 
-        u->auto_start_stop_ratelimit = (const RateLimit) {
-                10 * USEC_PER_SEC,
-                16
-        };
+        u->auto_start_stop_ratelimit = (const RateLimit) { .interval = 10 * USEC_PER_SEC, .burst = 16 };
 
         return u;
 }