DAOS-7485 control: Implement dmg system drain to act on all hosts

[tanabarr]

Add dmg system drain command to drain a set of storage nodes or ranks
from all the pools they belong too. Takes --ranks or --rank-hosts in
ranged format. Improve unit test coverage for lib/control, cmd/dmg and
server/mgmt_system system related functions.

Required-githooks: true

Before requesting gatekeeper:

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• Fix the commit message upon landing. Check the standard here. Edit it to create a single commit. If necessary, ask submitter for a new summary.

[github-actions]

Ticket title is 'dmg command to drain and reintegrate nodes from all pools'
Status is 'In Progress'
Labels: 'triaged'
https://daosio.atlassian.net/browse/DAOS-7485

[daosbuild1]

Test stage Unit Test on EL 8.8 completed with status UNSTABLE. https://build.hpdd.intel.com/job/daos-stack/job/daos//view/change-requests/job/PR-15506/1/testReport/

[daosbuild1]

Test stage Functional Hardware Medium Verbs Provider completed with status FAILURE. https://build.hpdd.intel.com//job/daos-stack/job/daos/view/change-requests/job/PR-15506/3/execution/node/1506/log

[tanabarr]

Documentation and functional tests to be added in subsequent PRs. Ping reviewers.

[daosbuild1]

Test stage Functional Hardware Medium Verbs Provider completed with status FAILURE. https://build.hpdd.intel.com//job/daos-stack/job/daos/view/change-requests/job/PR-15506/4/execution/node/1476/log