tidb-lightning: add checking PITR and active changefeed task

tidb-lightning/tidb-lightning-prechecks.md

@@ -19,3 +19,4 @@ The following table describes each check item and detailed explanation.
 | Recovery from breakpoints | >= 5.3.0 | This check ensures that no changes are made to the source file or schema in the database during the breakpoint recovery process that would result in importing the wrong data. |
 | Import into an existing table | >= 5.3.0 | When importing into an already created table, it checks, as much as possible, whether the source file matches the existing table. Check if the number of columns matches. If the source file has column names, check if the column names match. When there are default columns in the source file, it checks if the default columns have Default Value, and if they have, the check passes. |
 | Whether the target table is empty | >= 5.3.1 | TiDB Lightning automatically exits with an error if the target table is not empty. If parallel import mode is enabled (`parallel-import = true`), this check item will be skipped. |
+| Whether PITR is enabled or any changefeed task is running in the cluster | >= 6.5.0 | The TiDB Lightning physical import mode is incompatible with PITR and changefeed. If PITR is enabled or a changefeed task is running, TiDB Lightning automatically exits with an error. If you are certain that the tables to be imported do not require PITR or changefeed for replication, you can skip this check to proceed with the TiDB Lightning physical import mode. |