Add show details reminder in group search output

[vuil]

What this PR does / why we need it

Shows a notes at the bottom of the group search tabular output about using the --show-details flag to see all versions of the groups.

Which issue(s) this PR fixes

Fixes #

Describe testing done for PR

Added unit tests.

Output changes are as follows:

> tanzu plugin group search
  GROUP                       DESCRIPTION                          LATEST
  vmware-tanzucli/essentials  Essential plugins for the Tanzu CLI  v1.0.0
  vmware-tap/default          Plugins for TAP                      v1.7.3
  vmware-tkg/default          Plugins for TKG                      v2.4.1
  vmware-tmc/default          Plugins for TMC                      v1.0.0

Note: to view all plugin group versions available, use 'tanzu plugin group search --show-details'
>

Release note

Added note in "tanzu plugin group search" about using --show-details to see all versions of groups 

Additional information

Special notes for your reviewer

[marckhouzam]

One nit, and the release notes sentence seems either incomplete or has an extra in at the end.

Besides that LGTM