fix(grpc-loader): add new options by generic props loader

[wrspada02]

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?

The current grpc loader options for custom options has type any.

Issue Number: #13930

What is the new behavior?

This PR allows to pass generic type to the grpc loader options, and then, the custom options provided starts having type safety.

Does this PR introduce a breaking change?

• Yes
• No

[coveralls]

Pull Request Test Coverage Report for Build 01160bf8-86e1-4236-96a1-a9d868453463

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 92.213%

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Totals
Change from base Build 0b2170fc-d850-443a-8e46-397cb7d6d6fd:	0.0%
Covered Lines:	6750
Relevant Lines:	7320

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💛 - Coveralls