fix(types): stop before try to evaluate any as a path

[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?

Issue Number: fixes #906

What is the new behavior?

we can have keys with the type any when using ConfigService#get typed. See:

Does this PR introduce a breaking change?

• Yes
• No

Other information

The second commit is just a minor performance improvement not related with the original Issue. It was made to avoid computing PathImpl2<T> twice by using the infer keyword to cache the first result.
I can drop that commit if you prefer the old version in favor of readability.

[micalevisk]

ping @kamilmysliwiec this one should be pretty easy to review 😸

[kamilmysliwiec]

lgtm