DAOS-16924 dfs: new readdir API

[mchaarawi]

Add a new DFS readdir API that utilizes a new DFS anchor object which can be updated to include caching parameters for future calls. This API will be more useful when client side caching for readdir is implemented to access buckets of readdir entries.

Required-githooks: true

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[github-actions]

Ticket title is 'add readdir api that uses a new DFS anchor'
Status is 'Open'
https://daosio.atlassian.net/browse/DAOS-16924

[daosbuild1]

Test stage NLT on EL 8.8 completed with status UNSTABLE. https://build.hpdd.intel.com/job/daos-stack/job/daos//view/change-requests/job/PR-15687/1/testReport/

[daosbuild1]

Test stage NLT on EL 8.8 completed with status UNSTABLE. https://build.hpdd.intel.com/job/daos-stack/job/daos//view/change-requests/job/PR-15687/2/testReport/

[daosbuild1]

Test stage Functional on EL 8.8 completed with status UNSTABLE. https://build.hpdd.intel.com/job/daos-stack/job/daos//view/change-requests/job/PR-15687/3/testReport/

[daosbuild1]

Test stage Functional Hardware Large completed with status UNSTABLE. https://build.hpdd.intel.com/job/daos-stack/job/daos//view/change-requests/job/PR-15687/5/testReport/

[daosbuild1]

Test stage Unit Test on EL 8.8 completed with status FAILURE. https://build.hpdd.intel.com/job/daos-stack/job/daos/job/PR-15687/6/display/redirect