Support displayName on anonymous components

[urugator]

partial fix for #2721

Background:

For whatever reason, in react 17, getComponentName returns the name of the memoized component, rather than the name of the wrapper itself:
https://github.com/facebook/react/blob/12adaffef7105e2714f82651ea51936c563fe15c/packages/shared/getComponentName.js#L88
So how does displayName work on memoized component? Memoized component defines displayName as a getter/setter pair, where setter in addition to setting "own" name for the wrapper, also modifies the name of the original component:

const Original = function() {};
const Memoized = memo(Original);
Memoized.displayName = 'memoized';
console.log(Original.displayName === Memoized.displayName); // true

However it does it only if the original component does not have a name yet:

const Original = function() {};
Original.displayName = 'original'
const Memoized = memo(Original);
Memoized.displayName = 'memoized';
console.log(Original.displayName === Memoized.displayName); // false

In this case the Memoized.displayName is practically useless as it's ignored by devtools (you will see original in component tree).

Problem:

Setting displayName (by us) on either original or memoized component prevents customizing displayName by user.

Solution:

Since setting displayName is mostly relevant for anonymous functions, don't set displayName on these (we would set them to empty string anyway).
Additionally, don't hoist displayName as it would redefine memo's getter/setter.

Consequences

Component returned from observer does not have it's own displayName, but the wrapperComponent (available as .type) does, which should be sufficient.

[changeset-bot]

🦋 Changeset detected

Latest commit: 8191ca0

The changes in this PR will be included in the next version bump.

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mobx-react-lite	Patch

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[urugator]

@LandonSchropp added console.log("PR3192") at the beginning of observer, in case you wanna give it another try.
Dunno if necessary, but don't forget to remove the original deps, before linking your locals versions.