### What problem does this PR solve?
pick #43000
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Issue Number: close #xxx
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Problem Summary:
### Check List (For Committer)
- Test <!-- At least one of them must be included. -->
- [ ] Regression test
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nereids will parse function statement when replay create alias function,
when do parse, need to get sql mode and other variable. because replay
thread do not have connect context, NPE be thrown when parsing
### What problem does this PR solve?
Problem Summary:
There is a memory leak on FE side when continue running `export`
command.
The `ExportTaskExecutor` instances will be added to
`TransientTaskManager` and never be removed.
This PR mainly changes:
1. Remove unused `ExportTaskRegister` in `Env`.
2. Remove `ExportTaskExecutor` from `TransientTaskManager` once export
job is finished or cancelled.
### Release note
Fix FE memory leak by removing `ExportTaskExecutor` from
`TransientTaskManager` once export job is finished or cancelled.
pick:#42007
add Nereids GarbageCollect Time and Nereids BeFoldConst Time to profile
## Proposed changes
Issue Number: close #xxx
<!--Describe your changes.-->
pick from master #42576
intro by #39316. it want to fix a problem intro by #36699. but forgot to
remove all wrong code in #36699.
after #39316, we should not set offset on exchange, when the exchange is
on the top of a limit with offset.
## Proposed changes
1. Fix forward query exception if no status code is set in master
execution. EOF may result in this status.
2. Fix forward query stuck due to no result packet sent to mysql
channel. Should use result packets from master.
3. Fix potential forward query result loss if follower can read status
change during query process. Should judge by the status once before
execution.
4. Add assertion for regression test.
When dealing with a large number of tasks, the default execution queue
size is 1024. This can lead to tasks being dropped if the queue becomes
full.
eg
`dispatch instant task failed, job id is xxx`
To address this, you can add the parameters `insert_task_queue_size` and
`mtmv_task_queue_size` in the `fe.conf` configuration file. These
parameters must be set to a power of 2.
**Keep in mind, increasing this value is recommended only when thread
resources are limited; otherwise, you should consider increasing the
number of task execution threads.**
(cherry picked from commit f9ea8f8229e9f5514c1773bd25c3cc11985c63fb)
## Proposed changes
Issue Number: #42253
<!--Describe your changes.-->
Reverts apache/doris#42255
We have found that after closing the connection pool, there will be
class loading problems and connection release problems for some data
sources. We will remove this function first and re-add it after solving
and testing it completely.
