[chore](Nereids): rename pushdown to push_down

[jackwener]

Proposed changes

• rename pushdown to push_down

Further comments

If this is a relatively large or complex change, kick off the discussion at [email protected] by explaining why you chose the solution you did and what alternatives you considered, etc...

[jackwener]

run buildall

[jackwener]

run buildall

[doris-robot]

(From new machine)TeamCity pipeline, clickbench performance test result:
the sum of best hot time: 43.37 seconds
stream load tsv: 566 seconds loaded 74807831229 Bytes, about 126 MB/s
stream load json: 18 seconds loaded 2358488459 Bytes, about 124 MB/s
stream load orc: 65 seconds loaded 1101869774 Bytes, about 16 MB/s
stream load parquet: 32 seconds loaded 861443392 Bytes, about 25 MB/s
insert into select: 27.7 seconds inserted 10000000 Rows, about 361K ops/s
storage size: 17098799962 Bytes

[doris-robot]

TPC-H test result on machine: 'aliyun_ecs.c7a.8xlarge_32C64G'

Tpch sf100 test result on commit aca412260891c05a8019a8c546a9e4c93cec7ea7, data reload: false

run tpch-sf100 query with default conf and session variables
q1	4927	4638	4633	4633
q2	356	158	139	139
q3	2052	1893	1918	1893
q4	1385	1271	1230	1230
q5	3997	3971	4049	3971
q6	253	128	128	128
q7	1440	882	884	882
q8	2781	2802	2775	2775
q9	9595	9472	9621	9472
q10	3474	3528	3521	3521
q11	382	251	247	247
q12	441	283	291	283
q13	4567	3805	3783	3783
q14	332	282	286	282
q15	585	532	529	529
q16	667	591	588	588
q17	1146	985	964	964
q18	7849	7279	7352	7279
q19	1677	1659	1670	1659
q20	575	308	285	285
q21	4404	3918	3982	3918
q22	476	373	373	373
Total cold run time: 53361 ms
Total hot run time: 48834 ms

run tpch-sf100 query with default conf and set session variable runtime_filter_mode=off
q1	4604	4584	4604	4584
q2	348	230	260	230
q3	3998	4003	4001	4001
q4	2771	2699	2714	2699
q5	9592	9692	9660	9660
q6	246	123	125	123
q7	3033	2483	2458	2458
q8	4427	4455	4493	4455
q9	12928	12826	12790	12790
q10	4094	4169	4190	4169
q11	801	660	655	655
q12	970	816	813	813
q13	4271	3599	3543	3543
q14	376	365	356	356
q15	581	521	518	518
q16	740	669	690	669
q17	3938	3873	3902	3873
q18	9684	8947	8981	8947
q19	1848	1777	1794	1777
q20	2409	2086	2033	2033
q21	8795	8540	8539	8539
q22	900	802	787	787
Total cold run time: 81354 ms
Total hot run time: 77679 ms

[github-actions]

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

[github-actions]

PR approved by anyone and no changes requested.