https://github.com/apache/doris/pull/43500
### What problem does this PR solve?
Previously, sub_running_sink_operators was called only when encountering
EOS during sink
or when all sources were closed. However, this approach has issues, as
it’s possible
for the user to manually cancel, in which case there may be no EOS and
the sources may
not be closed. This would prevent running_sink_operators from reaching
zero, leading to errors.
```
PipelineTask[this = 0x7fc369fe9600, id = 0, open = true, eos = false, finish = false, dry run = false, elapse time = 26361.740784032s], block dependency = NULL, is running = true
operators:
LOCAL_EXCHANGE_OPERATOR (LOCAL_MERGE_SORT): id=-5, parallel_tasks=4, _channel_id: 0, _num_partitions: 4, _num_senders: 4, _num_sources: 4, _running_sink_operators: 1, _running_source_operators: 1, mem_usage: 0, data queue info: Data Queue 0: [size approx = 0, eos = false], MemTrackers: 0: 0, 1: 34537472, 2: 5701632, 3: 0,
DATA_STREAM_SINK_OPERATOR: id=6, Sink Buffer: (_should_stop = false, _busy_channels = 0, _is_finishing = false), _reach_limit: false
0. this=0x7fc376438f10, LOCAL_MERGE_EXCHANGE_OPERATOR_DEPENDENCY: id=-5, block task = 0, ready=true, _always_ready=true
0. this=0x7fc3764bc110, LOCAL_MERGE_EXCHANGE_OPERATOR_DEPENDENCY: id=-5, block task = 0, ready=true, _always_ready=true
0. this=0x7fc3764bc310, LOCAL_MERGE_EXCHANGE_OPERATOR_DEPENDENCY: id=-5, block task = 0, ready=true, _always_ready=true
0. this=0x7fc3764bc510, LOCAL_MERGE_EXCHANGE_OPERATOR_DEPENDENCY: id=-5, block task = 0, ready=true, _always_ready=true
```
- [x] Confirm test cases
- [x] Confirm document
- [x] Add branch pick label <!-- Add branch pick label that this PR
should merge into -->
261c65f72d