Migrate type tests to Vitest

[aryaemami59]

This PR:

• Converts typetest.ts file extensions to test-d.ts to be compatible with Vitest.
• Converts expectType() to either assertType() or expectTypeOf().toMatchTypeOf().
• Converts expectExactType to expectTypeOf().toEqualTypeOf().
• Converts lone-blocks to test or describe blocks.

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[markerikson]

Haven't paid any attention to this, I'm afraid :) Where's it stand? I see green.

Also, just out of curiosity, what's the net benefit of doing typetests with Vitest?

[aryaemami59]

@markerikson All tests are passing.

Also, just out of curiosity, what's the net benefit of doing typetests with Vitest?

1. Type tests become more semantic and easier to read.
2. We can take advantage of the type checking utilities Vitest provides.
3. We can use the .skip/.only/.todo syntax.
4. We can run both runtime and type tests by using the --typecheck flag.

On a side note I'm also a collaborator on the expect-type which is the library Vitest uses for type checking.

[markerikson]

Okay, cloned it briefly and confirmed A) it passes locally, B) it does catch errors if I introduce them. Nice!