GH-50440: [C++][Gandiva] fix out-of-bounds read in set_error_for_date

[Arawoof06]

Rationale for this change

set_error_for_date formats the invalid-date/timestamp message with snprintf(error, size, "%s%s", msg, input), but input is a Gandiva string passed as pointer plus length and is not NUL-terminated, so the %s conversion scans past the length bytes looking for a terminator and over-reads the values buffer (past its end for the last value). It is reached from castDATE_utf8/castTIMESTAMP_utf8 on any invalid CAST(str AS DATE/TIMESTAMP) input. Switching to the bounded %.*s form with the explicit length keeps the read inside the string, matching every other error formatter in the precompiled sources.

What changes are included in this PR?

Use %.*s with length in set_error_for_date, which covers all of its call sites in both castDATE_utf8 and castTIMESTAMP_utf8.

Are these changes tested?

Yes. Added TestTime.TestCastDateInvalidUnterminated, which feeds an invalid date held in an exactly-sized heap buffer with no trailing NUL so the over-read trips AddressSanitizer, and checks the error string is bounded to the input length.

Are there any user-facing changes?

No.

This PR contains a "Critical Fix". It fixes a heap out-of-bounds read reachable from user-supplied CAST-to-date/timestamp input.

• GitHub Issue: [C++][Gandiva] Out-of-bounds read when formatting invalid date/timestamp error messages #50440

[github-actions]

⚠️ GitHub issue #50440 has been automatically assigned in GitHub to PR creator.