feat(core): display class's name on request mapping exceptions

[micalevisk]

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)

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?

If we have an invalid controller class listed in some controllers array, we'll got this error:

What is the new behavior?

Now the error will looks like this:

Does this PR introduce a breaking change?

• Yes
• No

Other information

Also, I've leverage on this PR to increase the code coverage on /core/exceptions a bit as well because why not 🐱

before

now

[coveralls]

Pull Request Test Coverage Report for Build 7ab0292e-1fd4-425a-98f3-ce3c5d250a8e

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 93.804%

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Totals
Change from base Build a1f147f5-1d97-43a6-8bf9-8ee0113704c9:	0.02%
Covered Lines:	6116
Relevant Lines:	6520

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💛 - Coveralls