[chore](be) remove some unused code

[yiguolei]

What problem does this PR solve?

Issue Number: close #xxx

Related PR: #xxx

Problem Summary:

Release note

None

Check List (For Author)

• Test

  • Regression test
  • Unit Test
  • Manual test (add detailed scripts or steps below)
  • No need to test or manual test. Explain why:
    • This is a refactor/code format and no logic has been changed.
    • Previous test can cover this change.
    • No code files have been changed.
    • Other reason

• Behavior changed:

  • No.
  • Yes.

• Does this need documentation?

  • No.
  • Yes.

Check List (For Reviewer who merge this PR)

• Confirm the release note
• Confirm test cases
• Confirm document
• Add branch pick label

[hello-stephen]

Thank you for your contribution to Apache Doris.
Don't know what should be done next? See How to process your PR.

Please clearly describe your PR:

1. What problem was fixed (it's best to include specific error reporting information). How it was fixed.
2. Which behaviors were modified. What was the previous behavior, what is it now, why was it modified, and what possible impacts might there be.
3. What features were added. Why was this function added?
4. Which code was refactored and why was this part of the code refactored?
5. Which functions were optimized and what is the difference before and after the optimization?

[yiguolei]

run buildall

[doris-robot]

TPC-H: Total hot run time: 30658 ms

machine: 'aliyun_ecs.c7a.8xlarge_32C64G'
scripts: https://github.com/apache/doris/tree/master/tools/tpch-tools
Tpch sf100 test result on commit 752326888d9f6e93c6f7590bc2cf2d274da71d0e, data reload: false

------ Round 1 ----------------------------------
q1	17615	4476	4292	4292
q2	2086	343	233	233
q3	10116	1247	739	739
q4	10203	789	308	308
q5	7517	2199	1937	1937
q6	207	181	146	146
q7	896	745	613	613
q8	9290	1444	1142	1142
q9	4787	4661	4629	4629
q10	6824	1930	1561	1561
q11	502	289	302	289
q12	339	377	217	217
q13	17793	4081	3208	3208
q14	237	232	227	227
q15	882	812	813	812
q16	690	698	608	608
q17	689	862	495	495
q18	6631	5838	6165	5838
q19	1338	1079	768	768
q20	540	567	401	401
q21	2795	1910	1961	1910
q22	369	325	285	285
Total cold run time: 102346 ms
Total hot run time: 30658 ms

----- Round 2, with runtime_filter_mode=off -----
q1	4547	4561	4629	4561
q2	278	357	267	267
q3	2408	2904	2351	2351
q4	1497	1883	1437	1437
q5	4631	4634	4770	4634
q6	225	181	132	132
q7	1905	1886	1798	1798
q8	2576	2419	2367	2367
q9	7516	7503	7444	7444
q10	2729	3059	2566	2566
q11	554	455	493	455
q12	688	735	677	677
q13	3728	4047	3224	3224
q14	269	290	265	265
q15	822	776	774	774
q16	634	676	640	640
q17	1090	1322	1329	1322
q18	7426	7389	7354	7354
q19	834	800	802	800
q20	1940	2010	1870	1870
q21	4567	4246	4132	4132
q22	580	535	493	493
Total cold run time: 51444 ms
Total hot run time: 49563 ms

[doris-robot]

ClickBench: Total hot run time: 28.39 s

machine: 'aliyun_ecs.c7a.8xlarge_32C64G'
scripts: https://github.com/apache/doris/tree/master/tools/clickbench-tools
ClickBench test result on commit 752326888d9f6e93c6f7590bc2cf2d274da71d0e, data reload: false

query1	0.05	0.04	0.05
query2	0.09	0.04	0.05
query3	0.26	0.09	0.08
query4	1.61	0.11	0.11
query5	0.28	0.24	0.26
query6	1.17	0.68	0.67
query7	0.03	0.02	0.02
query8	0.06	0.04	0.04
query9	0.57	0.50	0.50
query10	0.55	0.54	0.55
query11	0.14	0.10	0.09
query12	0.14	0.10	0.11
query13	0.62	0.62	0.62
query14	1.09	1.07	1.05
query15	0.86	0.87	0.87
query16	0.41	0.41	0.38
query17	1.14	1.10	1.15
query18	0.22	0.21	0.21
query19	2.11	1.89	1.98
query20	0.02	0.01	0.02
query21	15.42	0.25	0.15
query22	5.09	0.05	0.05
query23	15.72	0.28	0.10
query24	2.65	0.63	0.97
query25	0.09	0.05	0.08
query26	0.14	0.13	0.14
query27	0.08	0.06	0.05
query28	5.21	1.14	0.96
query29	12.58	3.93	3.15
query30	0.28	0.13	0.12
query31	2.83	0.63	0.40
query32	3.23	0.60	0.50
query33	3.26	3.28	3.22
query34	16.24	5.41	4.68
query35	4.85	4.78	4.76
query36	0.62	0.49	0.49
query37	0.11	0.08	0.06
query38	0.07	0.05	0.04
query39	0.04	0.03	0.03
query40	0.19	0.16	0.15
query41	0.09	0.03	0.02
query42	0.05	0.03	0.02
query43	0.04	0.03	0.04
Total cold run time: 100.3 s
Total hot run time: 28.39 s

[doris-robot]

BE UT Coverage Report

Increment line coverage 🎉

Increment coverage report
Complete coverage report

Category	Coverage
Function Coverage	52.62% (19411/36892)
Line Coverage	36.15% (180717/499953)
Region Coverage	32.46% (140004/431254)
Branch Coverage	33.48% (60635/181089)

[hello-stephen]

BE Regression && UT Coverage Report

Increment line coverage 100% (0/0) 🎉

Increment coverage report
Complete coverage report

Category	Coverage
Function Coverage	71.63% (25895/36153)
Line Coverage	54.26% (270600/498729)
Region Coverage	51.50% (224369/435638)
Branch Coverage	53.08% (96500/181797)

[Copilot]

Pull request overview

Removes dead code and tightens immutability in the BE codebase by eliminating unused RowCursor key-building helpers and making a runtime-filter flag immutable.

Changes:

• Make RuntimeFilter::_has_remote_target a const bool (initialized via the existing constructor initializer list).
• Remove unused RowCursor::build_max_key() / RowCursor::build_min_key() declarations and definitions.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
be/src/runtime_filter/runtime_filter.h	Makes the remote-target flag immutable (const) while preserving constructor initialization.
be/src/olap/row_cursor.h	Removes unused build_max_key / build_min_key APIs from the public interface.
be/src/olap/row_cursor.cpp	Removes unused implementations of build_max_key / build_min_key.

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[github-actions]

PR approved by at least one committer and no changes requested.

[github-actions]

PR approved by anyone and no changes requested.