[Enhancement] add limit operator before union gather

[stdpain]

Why I'm doing:

baseline:

mysql>   select  to_bitmap(1) FROM TABLE(generate_series(0, 655350)) union all select bitmap_agg(lo_orderkey) from lineorder group by lo_linenumber limit 1;
+--------------+
| to_bitmap(1) |
+--------------+
| NULL         |
+--------------+
1 row in set (7.42 sec)

patched:

mysql> select  to_bitmap(1) FROM TABLE(generate_series(0, 655350)) union all select bitmap_agg(lo_orderkey) from lineorder group by lo_linenumber limit 1;
+--------------+
| to_bitmap(1) |
+--------------+
| NULL         |
+--------------+
1 row in set (0.04 sec)

What I'm doing:

Fixes #issue

What type of PR is this:

• [ ] BugFix
• [ ] Feature
• [x] Enhancement
• [ ] Refactor
• [ ] UT
• [ ] Doc
• [ ] Tool

Does this PR entail a change in behavior?

• [ ] Yes, this PR will result in a change in behavior.
• [x] No, this PR will not result in a change in behavior.

If yes, please specify the type of change:

• [ ] Interface/UI changes: syntax, type conversion, expression evaluation, display information
• [ ] Parameter changes: default values, similar parameters but with different default values
• [ ] Policy changes: use new policy to replace old one, functionality automatically enabled
• [ ] Feature removed
• [ ] Miscellaneous: upgrade & downgrade compatibility, etc.

Checklist:

• [x] I have added test cases for my bug fix or my new feature
• [ ] This pr needs user documentation (for new or modified features or behaviors)
  • [ ] I have added documentation for my new feature or new function
• [ ] This is a backport pr

Bugfix cherry-pick branch check:

• [x] I have checked the version labels which the pr will be auto-backported to the target branch
  • [x] 3.4
  • [x] 3.3
  • [ ] 3.2
  • [ ] 3.1
  • [ ] 3.0

[github-actions[bot]]

[FE Incremental Coverage Report]

:white_check_mark: pass : 0 / 0 (0%)

[github-actions[bot]]

[Java-Extensions Incremental Coverage Report]

:white_check_mark: pass : 0 / 0 (0%)

[github-actions[bot]]

[BE Incremental Coverage Report]

:white_check_mark: pass : 4 / 4 (100.00%)

file detail

	path	covered_line	new_line	coverage	not_covered_line_detail
:large_blue_circle:	be/src/exec/union_node.cpp	4	4	100.00%	[]

[github-actions[bot]]

@Mergifyio backport branch-3.4

[github-actions[bot]]

@Mergifyio backport branch-3.3

[mergify[bot]]

backport branch-3.4

✅ Backports have been created

* [#53120 [Enhancement] add limit operator before union gather (backport #53102)](https://github.com/StarRocks/starrocks/pull/53120) has been created for branch `branch-3.4`

[mergify[bot]]

backport branch-3.3

✅ Backports have been created

* [#53121 [Enhancement] add limit operator before union gather (backport #53102)](https://github.com/StarRocks/starrocks/pull/53121) has been created for branch `branch-3.3`