daos DAOS-17561 object: Force SGL copies for fetch when IOV buffer length exceeds requested length

Some applications may allocate larger IOV buffers than the requested length for fetch operations. By trimming SGL iov_buf_len to match iov_len and enforcing SGL copies during fetching, we can significantly reduce latency.### Steps for the author:

[ ] Commit message follows the guidelines.
[ ] Appropriate Features or Test-tag pragmas were used.
[ ] Appropriate Functional Test Stages were run.
[ ] At least two positive code reviews including at least one code owner from each category referenced in the PR.
[ ] Testing is complete. If necessary, forced-landing label added and a reason added in a comment.

After all prior steps are complete:

[ ] Gatekeeper requested (daos-gatekeeper added as a reviewer).

May 14 '25 14:05 wangshilong

Errors are component not formatted correctly,Title of PR is too long,Ticket number prefix incorrect,PR title is malformatted. See https://daosio.atlassian.net/wiki/spaces/DC/pages/11133911069/Commit+Comments,Unable to load ticket data https://daosio.atlassian.net/browse/

May 14 '25 14:05 github-actions[bot]

Test stage Unit Test on EL 8.8 completed with status FAILURE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net/job/daos-stack/job/daos/job/PR-16383/2/display/redirect

Jul 08 '25 14:07 daosbuild3

Test stage Unit Test bdev on EL 8.8 completed with status FAILURE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net/job/daos-stack/job/daos/job/PR-16383/2/display/redirect

Jul 08 '25 14:07 daosbuild3

Test stage Unit Test bdev with memcheck on EL 8.8 completed with status FAILURE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net/job/daos-stack/job/daos/job/PR-16383/2/display/redirect

Jul 08 '25 14:07 daosbuild3

Test stage Unit Test with memcheck on EL 8.8 completed with status FAILURE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net/job/daos-stack/job/daos/job/PR-16383/2/display/redirect

Jul 08 '25 14:07 daosbuild3

Test stage NLT on EL 8.8 completed with status FAILURE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net/job/daos-stack/job/daos/job/PR-16383/2/display/redirect

Jul 08 '25 14:07 daosbuild3

Test stage Functional on EL 8.8 completed with status UNSTABLE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net/job/daos-stack/job/daos//view/change-requests/job/PR-16383/3/testReport/

Jul 10 '25 16:07 daosbuild3

Test stage Functional on EL 8.8 completed with status UNSTABLE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net/job/daos-stack/job/daos//view/change-requests/job/PR-16383/5/testReport/

Jul 23 '25 09:07 daosbuild3

Test stage Functional on EL 8.8 completed with status UNSTABLE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net/job/daos-stack/job/daos//view/change-requests/job/PR-16383/6/testReport/

Jul 26 '25 05:07 daosbuild3

Test stage Functional on EL 8.8 completed with status UNSTABLE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net/job/daos-stack/job/daos//view/change-requests/job/PR-16383/7/testReport/

Jul 31 '25 22:07 daosbuild3

Test stage NLT on EL 8.8 completed with status UNSTABLE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net/job/daos-stack/job/daos//view/change-requests/job/PR-16383/10/testReport/

Aug 28 '25 09:08 daosbuild3

Test stage Functional on EL 8.8 completed with status FAILURE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net//job/daos-stack/job/daos/view/change-requests/job/PR-16383/10/execution/node/1254/log

Aug 28 '25 12:08 daosbuild3

Test stage Functional on EL 8.8 completed with status UNSTABLE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net/job/daos-stack/job/daos//view/change-requests/job/PR-16383/11/testReport/

Aug 28 '25 21:08 daosbuild3

Test stage Functional on EL 8.8 completed with status UNSTABLE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net/job/daos-stack/job/daos//view/change-requests/job/PR-16383/13/testReport/

Dec 09 '25 09:12 daosbuild3