oc-mirror requires that an operator's default channel is included in the ImageSetConfiguration

Issue

• Is it possible to not mirror the default channel of an operator when using oc-mirror?

• When using an older version of oc-mirror, the following error is shown:

  The rendered catalog is invalid.
  
  Run "oc-mirror list operators --catalog CATALOG-NAME --package PACKAGE-NAME" for more information.
  
  Please check the minVersion, maxVersion, and default channel for each invalid package.
  error: error converting declarative config to include config: invalid index:
  └── invalid package "example-operator":
    └── invalid channel "stable":
        └── channel must contain at least one bundle
  

• When using a newer version of oc-mirror, an error similar to the following is shown:

  The current default channel was not valid, so an attempt was made to automatically assign a new default channel, which has failed.
  The failure occurred because none of the remaining channels contain a "olm.channel" priority property, so it was not possible to establish a channel to use as the default channel.
  
  This can be resolved by one of the following changes:
  1) assign a "olm.channel" property on the appropriate channels to establish a channel priority
  2) modify the default channel manually in the catalog
  3) by changing the ImageSetConfiguration to filter channels or packages in such as way that it will include a package version that exists in the current default channel
  
  The rendered catalog is invalid.
  
  Run "oc-mirror list operators --catalog CATALOG-NAME --package PACKAGE-NAME" for more information.
  
  error: error generating diff: the current default channel "latest" for package "example-operator" could not be determined... ensure that your ImageSetConfiguration filtering criteria results in a package version that exists in the current default channel