refactor(core): env variable to control slow threshold of token factory

[H4ad]

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?

Today, there's no way to change the threshold we added for slow serialization.

Refs: #12738 (comment)

What is the new behavior?

Now, we can control the amount of time in MS using NEST_TOKEN_FACTORY_SLOW_THRESHOLD_MS

Does this PR introduce a breaking change?

• Yes
• No

Other information

[coveralls]

Pull Request Test Coverage Report for Build ecf984e0-9894-4582-afce-61a77c6239da

Details

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.001%) to 92.209%

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Totals
Change from base Build 7ea6f01d-9fcc-4d6c-90b4-f217d2306325:	0.001%
Covered Lines:	6746
Relevant Lines:	7316

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💛 - Coveralls

[kazazor]

Looks simple and effective, thank you!

[kazazor]

Hi @H4ad , thank you so much for making this PR! Indeed, this warning is driving us crazy today :)

Is anything blocking you from merging it and having it in the next patch version of NestJS? Would be great to have it