Introduce inferrable TConfig

[Andarist]

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[Andarist]

Unfortunately, it deoptimizes when typed invokes are involved. I prepared a minimal repro case here: TS playground

[Andarist]

Ok, so I couldn't resist and I peeked under the hood to see what is being inferred in the first pass internally. It seems that we run into the same problem as we were running before. The problem was just more apparent before because we ended up with a visible error. Now the problem is still there but it gets somewhat swallowed. The invoke.src property widens to string within the inferred TConfig and then it fails the constraint check. We can observe the error if we provide the computed inference candidates directly as type arguments here: TS playground

And this is actually fixable using the trick that I applied in one of those previous PRs: TS playground.

(but I still think this is a post-release item)

[Andarist]

Superseded by #4498