dump the list of available bundles (and extension alaises) if no name is provided
merged branch lsmith77/config_dump_ref_list_bundles (PR #7578)

This PR was submitted for the 2.1 branch but it was merged into the master branch instead (closes #7578).

Discussion
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dump the list of available bundles (and extension alaises) if no name is provided

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

Not sure if this should only go into master or if such a small tweak can also go into 2.1 or at least 2.2

Commits
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2ba6fca dump the list of available bundles (and extension alaises) if no name is provided