DPE-7726: Stop deffering for non-joined peers on on_start/on_config_changed

Those defers are necessary to support scale-up/scale-down during the refresh,
while they have significalty slowdown PostgreSQL 16 bootstrap (and other
daily related mainteinance tasks, like re-scaling, full node reboot/recovery, etc).

Muting them for now with the proper documentation record to
forbid rescaling during the refresh, untli we minimise amount of defers in PG16.
Throw and warning for us to recall this promiss.

Author: taurus-forever

src/charm.py

@@ -1428,10 +1428,8 @@ def _on_config_changed(self, event) -> None:  # noqa: C901
             return
 
         if self.refresh is None:
-            logger.debug("Defer on_config_changed: Refresh could be in progress")
-            event.defer()
-            return
-        if self.refresh.in_progress:
+            logger.warning("Warning _on_config_changed: Refresh could be in progress")
+        elif self.refresh.in_progress:
             logger.debug("Defer on_config_changed: Refresh in progress")
             event.defer()
             return
@@ -1553,10 +1551,8 @@ def _can_start(self, event: StartEvent) -> bool:
 
         # Safeguard against starting while refreshing.
         if self.refresh is None:
-            logger.debug("Defer on_start: Refresh could be in progress")
-            event.defer()
-            return False
-        if self.refresh.in_progress:
+            logger.warning("Warning on_start: Refresh could be in progress")
+        elif self.refresh.in_progress:
             # TODO: we should probably start workload if scale up while refresh in progress
             logger.debug("Defer on_start: Refresh in progress")
             event.defer()