feat(@nestjs/swagger): defaults api tag to controller name

[nhomble]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

comment was added, but I'll follow up with actual doc update if they approach looks good

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

What is the current behavior?

controller names are ignored

Issue Number: 3011

What is the new behavior?

users can opt-in to have the controller name be added to the tag list

Does this PR introduce a breaking change?

• Yes
• No

it's opt-in

Other information

[nhomble]

from the manual test

we don't dedupe in case the dev explicitly adds more tags

[nhomble]

@kamilmysliwiec do you prefer to do feedback in github or should I join discord?

If the changes (especially the config parameter) look good, I'll update the docs!

[nhomble]

I'm going to follow up this week with doc changes.

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Followed up