docs: clarify hotplug-hook subcommands in CLI reference

[kaivshah]

The CLI reference lists query, handle, and enable as top-level cloud-init subcommands, but they're actually subcommands of devel hotplug-hook (see cloudinit/cmd/devel/hotplug_hook.py), each requiring --subsystem. This also caused the doc's query heading to collide with the real top-level query command later on the same page. This PR nests them correctly under devel hotplug-hook with accurate example invocations.

Proposed Commit Message

<type>(optional scope): <summary>  # no more than 72 characters

A description of what the change being made is and why it is being
made if the summary line is insufficient.  This should be wrapped at
72 characters.

If you need to write multiple paragraphs, feel free.

Fixes GH-NNNNN (GitHub Issue number. Remove line if irrelevant)
LP: #NNNNNN (Launchpad bug number. Remove line if irrelevant)

Additional Context

Test Steps

Merge type

• Squash merge using "Proposed Commit Message"
• Rebase and merge unique commits. Requires commit messages per-commit each referencing the pull request number (#<PR_NUM>)