make defineTypekit resilient to multiple version loaded

Problem is righht now we define the typekit prototype as
```ts
export const TypekitPrototype: Record = {};
```
This object of course would be different if a different version of the `@typespec/compiler` is loaded and the typekits would get registered separately causing errors.

## Solution

1. Check how vitest deals with the custom matchers https://vitest.dev/guide/extending-matchers and see if they do handle this case(might not)
2. A solution we can do is replace `{}` with a `globalThis[Symbol.for('TypeSpec.TypeKitProto')]`