info subcommand

[tedteng]

What this PR does / why we need it:

Garden: dev-local
Seed                                  Total                    Active                    Hibernated                    Allocatable                    Capacity
----                                  -----                    ------                    ----------                    -----------                    --------
alicloud                              10                       5                         4                             250                            250
aws                                   10                       1                         9                             250                            250
----                                  -----                    ------                    ----------                    -----------                    --------
TOTAL                                 20                       6                        13                           -                              -
Unscheduled                           1
Unscheduled List                    abc123,

Which issue(s) this PR fixes: Fixes https://github.com/gardener/gardenctl-v2/issues/137

Special notes for your reviewer:

Release note:

Get landscape informations and shows the number of shoots per seed, e.g. "gardenctl info"

[tedteng]

PR ready and feel free to review it thanks @gardener/gardenctl-v2-maintainers

[tedteng]

rebased, PR ready for review

[tedteng]

PR is rebased and ready and feel free to review it thanks. @gardener/gardenctl-v2-maintainers

[tedteng]

PR is rebased and feel free to process it thanks. @gardener/gardenctl-v2-maintainers

[gardener-robot]

@tedteng You need rebase this pull request with latest master branch. Please check.

[tedteng]

/close as no longer required.