[Bug](load) INSERT SELECT data invisible after quorum success with cancelled node channel

### Problem
When `INSERT INTO ... SELECT ...` writes to multiple replicas, if one node channel is slow and times out during `close_wait`, it gets cancelled but NOT marked as failed. This causes:

1. `close_wait` returns OK even though a node was cancelled
2. FE is unaware of the failure, commits the transaction
3. PUBLISH_VERSION task is sent to ALL nodes including the cancelled one
4. Cancelled node can't find the rowset → publish fails
5. Data stays COMMITTED but not VISIBLE for a long time (30+ minutes until retry)

### Root Cause
In `IndexChannel::close_wait()` (vtablet_writer.cpp), when unfinished node channels are cancelled due to timeout, `mark_as_failed()` is not called. FE receives no error tablet info for the cancelled replicas.

### Fix
After cancelling unfinished node channels in `close_wait` timeout:
1. Call `mark_as_failed()` to record failed tablets
2. Call `check_intolerable_failure()` - if failures exceed tolerance, fail the entire load
3. Call `set_error_tablet_in_state()` to propagate error info to FE

This allows FE to:
- Skip failed replicas during PUBLISH_VERSION
- Data becomes visible immediately on healthy replicas
- Background TabletScheduler auto-repairs the failed replica

### Behavior after fix
| Scenario | Replicas | Result |
|----------|----------|--------|
| 3 replicas, 1 timeout | 2/3 success | ✅ Publish succeeds, failed replica auto-repairs |
| 3 replicas, 2 timeout | 1/3 success | ❌ Load fails, user gets error |