kn source list-types; plugin support, column for built-in source check

[navidshaikh]

In what area(s)?

eventing

Classifications:

/kind feature

Describe the feature:

Part of #511

• Plugin support
• Add a column to output for showing whether the source is built-in or otherwise.

[github-actions]

This issue is stale because it has been open for 90 days with no
activity. It will automatically close after 30 more days of
inactivity. Reopen the issue with /reopen. Mark the issue as
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[navidshaikh]

/remove-lifecycle stale

[github-actions]

This issue is stale because it has been open for 90 days with no
activity. It will automatically close after 30 more days of
inactivity. Reopen the issue with /reopen. Mark the issue as
fresh by adding the comment /remove-lifecycle stale.