[scheduler] Force-inline process_defer_queue_() fast path

process_defer_queue_() follows the same fast-path/slow-path pattern
as cleanup_() and process_to_add(): an atomic load + branch that
skips to the slow path only when work is pending. GCC currently
inlines it, but past experience shows the compiler can change its
mind when surrounding code changes. Use ESPHOME_ALWAYS_INLINE to
lock in the intended behavior.

esphome/core/scheduler.h

@@ -407,7 +407,7 @@ class Scheduler {
   // Process defer queue for FIFO execution of deferred items.
   // IMPORTANT: This method should only be called from the main thread (loop task).
   // Inlined: the fast path (nothing deferred) is just an atomic load check.
-  inline void HOT process_defer_queue_(uint32_t &now) {
+  inline void ESPHOME_ALWAYS_INLINE HOT process_defer_queue_(uint32_t &now) {
     // Fast path: nothing to process, avoid lock entirely.
     // Worst case is a one-loop-iteration delay before newly deferred items are processed.
     if (this->defer_empty_())