DAOS-18304 ddb: Add unit test to ddb code

[knard38]

Description

This PR introduce some code refactoring of the DDB code, for being able to add some unit and integration tests to the DBB go code:

• The GO interface DdbApi is introduced to allow the use of GO test stub.
• Refactor initialisation of the C structure from the Go Code to allow the use of GO test stub.
• The useless C attributes dc_pool_path and dc_db_path are removed.

It also fixes miscellaneous issues:

• Remove invalid restrictions on pool file path size.
• Improper cleanup of the function ddb_run_feature().
• Add db_path parameter to Pool destroy command.
• Fix invalid return code with non-interactive mode

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).

[github-actions]

Ticket title is 'Add unit test to ddb go code'
Status is 'In Progress'
https://daosio.atlassian.net/browse/DAOS-18304

[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-17464/1/testReport/

[daosbuild3]

Test stage Functional Hardware Medium MD on SSD completed with status FAILURE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net//job/daos-stack/job/daos/view/change-requests/job/PR-17464/1/execution/node/1358/log

[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-17464/3/testReport/

[daosbuild3]

Test stage Functional Hardware Medium MD on SSD completed with status FAILURE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net//job/daos-stack/job/daos/view/change-requests/job/PR-17464/3/execution/node/1314/log

[daosbuild3]

Test stage Functional Hardware Medium Verbs Provider MD on SSD completed with status FAILURE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net/job/daos-stack/job/daos/job/PR-17464/4/display/redirect

[daosbuild3]

Test stage Functional Hardware Medium MD on SSD completed with status FAILURE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net//job/daos-stack/job/daos/view/change-requests/job/PR-17464/4/execution/node/1352/log

[daosbuild3]

Test stage Build on EL 9.6 completed with status FAILURE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net//job/daos-stack/job/daos/view/change-requests/job/PR-17464/5/execution/node/266/log

[daosbuild3]

Test stage Build 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-17464/5/execution/node/274/log

[daosbuild3]

Test stage Build on Leap 15.5 with Intel-C and TARGET_PREFIX completed with status FAILURE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net//job/daos-stack/job/daos/view/change-requests/job/PR-17464/5/execution/node/318/log

[daosbuild3]

Test stage Build on Leap 15.5 completed with status FAILURE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net//job/daos-stack/job/daos/view/change-requests/job/PR-17464/5/execution/node/406/log

[daosbuild3]

Test stage Unit Test 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-17464/6/testReport/