fix(computedAsync): keep evaluating true for concurrent changes

[bodograumann]

Description

When the async computation in computedAsync finish out-of-order, all but the result for the final value are discarded.
This works fine, but was previously untested afaics.
The status ref evaluating which tracks, whether a computation is currently running, was however already set to false when any computation finished, even though others were still in progress.

I have added a test which checks both and fixed the problem with evaluating, so it is now only false after the computation for the latest dependency value(s) has finished.

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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