Replace isArray.js with native Array.isArray function

[fredj]

Related to #8515, Array.isArray is supported since IE 9

[cesium-concierge]

Thanks for the pull request @fredj!

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[hpinkos]

This sounds good to me. @shunter can you think of a reason we should keep around our polyfills like this? Old version of IE that don't have support for Array.isArray have been out of support for a while.

[fredj]

@hpinkos I've wrote that the module will be removed in version 1.69; it is correct? And I guess that a new issue should be created for the actual removal.

[shunter]

can you think of a reason we should keep around our polyfills like this?

Matt's comment in #4554 is still the main reason. I checked and we don't currently use isArray at the top-level (i.e. called when the script is included) so I don't think this will affect anything.

[mramato]

@fredj please merge in master and then we'll merge this up. Thanks again.

[fredj]

Thanks @mramato, master is now merged

[fredj]

ping @mramato

[mramato]

Thanks.