fix #210 by including psalm-* annotations to ArrayCollection#map()

[someniatko]

Apparently, psalm cannot reuse @psalm-template from parent's method declaration using @inheritdoc, so we cannot just specify @psalm-return static<TKey, U>.

Fixes #210

[Ocramius]

@muglug can I please get your opinion, before we go ahead and repeat docblocks in inheritance trees?

[muglug]

Looks good to me!

[muglug]

Psalm sees @return static and that always takes precedence over something inherited. This PR will fix the return type.

[Ocramius]

Thanks @someniatko!

[someniatko]

@muglug @Ocramius I have no idea why, but this issue still reproduces itself on https://github.com/someniatko/doctrine-collections-map-psalm

I found out that if in

    /**
     * @return static
     *
     * @psalm-template U
     * @psalm-param Closure(T=):U $func
     * @psalm-return static<TKey, U>
     */
    public function map(Closure $func)

I replace static with ArrayCollection in psalm-return annotation, psalm does no longer find errors.
I believe this is a bug in psalm.

psalm 3.6.4
doctrine/collections 1.6.3