clustercatalog content discovery for packages and bundle versions

[ankitathomas]

Adds a new command to list contents of available, healthy ClusterCatalogs.

Addresses operator-framework/operator-controller#1768

$ kubectl operator olmv1 search catalog  --help
Search catalogs for installable operators matching parameters

Usage:
  operator olmv1 search catalog [flags]

Aliases:
  catalog, catalogs

Flags:
      --catalog string              Catalog to search on. If not provided, all available catalogs are searched.
      --catalogd-namespace string   Namespace for the catalogd controller (default "olmv1-system")
  -h, --help                        help for catalog
      --list-versions               List all versions available for each package
  -o, --output string               output format. One of: (yaml|json)
      --package string              Search for package by name. If empty, all available packages will be listed
  -l, --selector string             Selector (label query) to filter catalogs on, supports '=', '==', and '!='
      --timeout string              Timeout for fetching catalog contents (default "5m")

Global Flags:
  -n, --namespace string   If present, namespace scope for this CLI request
ankithom@ankithom-thinkpadt14sgen2i:~/go/src/github.com/operator-framework/ku

By default, the command lists all available packages and channels from all catalogs present on cluster. --timeout can be modified to support listing large catalogs.

$ kubectl operator olmv1 search catalog 
PACKAGE                                   CATALOG        PROVIDER  CHANNELS
accuknox-operator                         operatorhubio            stable
aerospike-kubernetes-operator             operatorhubio            alpha,stable
...

The command also supports listing available bundle versions with `--list-versions`
```bash
$ kubectl operator olmv1 search catalog --list-versions
PACKAGE                                   CATALOG        PROVIDER                            VERSION
accuknox-operator                         operatorhubio  Accuknox Inc.                       0.7.1
ack-acm-controller                        operatorhubio  Amazon, Inc.                        1.1.1
ack-acm-controller                        operatorhubio  Amazon, Inc.                        1.1.0

The queried catalogs can be restricted via a label selector, specified by --selector, and the output can be restricted to a specific package with --package.

Currently supports yaml and json outputs for the catalog FBC, in addition to the table output.