fix: make IndexSearch optimization log reasons why it may refuse to u… (#524)

* fix: make IndexSearch optimization log reasons why it may refuse to use a replacement task

* style: pre-commit.ci auto fixes [...]

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: bhearsum

src/taskgraph/optimize/strategies.py

@@ -49,11 +49,17 @@ def should_replace_task(self, task, params, deadline, arg):
                 # status can be `None` if we're in `testing` mode
                 # (e.g. test-action-callback)
                 if not status or status.get("state") in ("exception", "failed"):
+                    logger.debug(
+                        f'not replacing {task["label"]} with {task_id} because it is in failed or exception state'
+                    )
                     continue
 
                 if deadline and datetime.strptime(
                     status["expires"], self.fmt
                 ) < datetime.strptime(deadline, self.fmt):
+                    logger.debug(
+                        f'not replacing {task["label"]} with {task_id} because it expires before {deadline}'
+                    )
                     continue
 
                 return task_id