Improvements to P.infer and isMatching

[gvergnaud]

This release contains two changes:

Typecheck pattern when using isMatching with 2 parameter.

It used to be possible to pass a pattern than could never match to isMatching. The new version checks that the provide pattern does match the value in second parameter:

type Pizza = { type: 'pizza'; topping: string };
type Sandwich = { type: 'sandwich'; condiments: string[] };
type Food = Pizza | Sandwich;

const fn = (food: Pizza | Sandwich) => {
    if (isMatching({ type: 'oops' }, food)) {
        //                  👆 used to type-check, now doesn't!
    }
}

Do not use P.infer as an inference point

When using P.infer<Pattern> to type a function argument, like in the following example:

const getWithDefault = <T extends P.Pattern>(
  input: unknown,
  pattern: T,
  defaultValue: P.infer<T> //  👈
): P.infer<T> =>
  isMatching(pattern, input) ? input : defaultValue

TypeScript could get confused and find type errors in the wrong spot:

const res = getWithDefault(null, { x: P.string }, 'oops') 
//                                     👆           👆 type error should be here
//                                 but it's here 😬

This PR fixes this problem