Do not hide remapped subcommands

[marckhouzam]

What this PR does / why we need it

If the plugin's descriptor's Hidden field is set to true, only the root command of the plugin should be hidden while any mapped subcommands should stay visible.

Which issue(s) this PR fixes

Fixes #830

Describe testing done for PR

I tested with a plugin that set the descriptor's Hidden field to true, and remaps a subcommand.

$ tz rbac info | jq
{
  "name": "rbac",
 [...]
 "hidden": true,
  "completionType": 0,
  "commandMap": [
    {
      "srcPath": "role",
      "dstPath": "role",
      "overrides": "",
      "description": "Tanzu Platform Role-Based Access Control",
      "aliases": [
        "roles"
      ]
    }
  ],
  "pluginRuntimeVersion": "v1.4.3",
  "binaryArch": "arm64"
}

# Notice that the role command is visible and that the rbac command is hidden
# Before this fix, the role command was also hidden
$ tz -h | egrep 'rbac|role'
    role                    Tanzu Platform Role-Based Access Control

Release note

Do not hide remapped subcommands when the plugin's root command is hidden.

Additional information

Special notes for your reviewer

[vuil]

LGTM.
Nice clean fix and tests.
Thanks for reporting and fixing the issue !