[scheduler] Force-inline cleanup_() fast path into Scheduler::call()

cleanup_() has a two-line fast path (check to_remove count, return
!items_.empty()) with the slow path already out-of-line in
cleanup_slow_path_(). Despite `inline` hint, GCC on Xtensa emits it
as a separate function, adding unnecessary call overhead on every
Scheduler::call() invocation even when there is nothing to clean up.

Use ESPHOME_ALWAYS_INLINE to guarantee inlining. Verified on ESP8266:
- cleanup_() symbol eliminated from binary
- Scheduler::call() grows 4 bytes (inlined fast path)
- Net savings: 23 bytes (27-byte out-of-line body removed)
- Idle loop path: 1 out-of-line call instead of 2

esphome/core/scheduler.h

@@ -302,7 +302,7 @@ class Scheduler {
   // loop thread structurally modifies items_ (push/pop/erase). Other threads may
   // iterate items_ and mark items removed under lock_, but never change the
   // vector's size or data pointer.
-  inline bool HOT cleanup_() {
+  inline bool ESPHOME_ALWAYS_INLINE HOT cleanup_() {
     if (this->to_remove_empty_())
       return !this->items_.empty();
     return this->cleanup_slow_path_();