[Fix](from_unixtime) Keep consistent with MySQL & bug fix (#25966)

[jackwener]

Proposed changes

Bug fix: implicit convert from int32 -> int64 makes negative time stamp valid, so change signature to int64
Consistent: keep consistent with mysql.

(cherry picked from commit 0449a24)

Further comments

If this is a relatively large or complex change, kick off the discussion at dev@doris.apache.org by explaining why you chose the solution you did and what alternatives you considered, etc...

[github-actions]

clang-tidy review says "All clean, LGTM! 👍"

[jackwener]

run buildall

[doris-robot]

TeamCity be ut coverage result:
Function Coverage: 37.81% (7993/21139)
Line Coverage: 29.49% (64913/220085)
Region Coverage: 28.97% (33401/115291)
Branch Coverage: 24.84% (17140/68988)
Coverage Report: http://coverage.selectdb-in.cc/coverage/94da51d1de3245999ca60c89d5da4bd0e4264db7_94da51d1de3245999ca60c89d5da4bd0e4264db7/report/index.html

[doris-robot]

(From new machine)TeamCity pipeline, clickbench performance test result:
the sum of best hot time: 51.25 seconds
stream load tsv: 575 seconds loaded 74807831229 Bytes, about 124 MB/s
stream load json: 20 seconds loaded 2358488459 Bytes, about 112 MB/s
stream load orc: 66 seconds loaded 1101869774 Bytes, about 15 MB/s
stream load parquet: 32 seconds loaded 861443392 Bytes, about 25 MB/s
insert into select: 29.9 seconds inserted 10000000 Rows, about 334K ops/s
storage size: 17162380326 Bytes

[xiaokang]

#25966