[5.2] Minor cleanup for plugins JS

[C-Lodder]

Summary of Changes

As Joomla no longer supports IE11, this PR mainly removes the need for converting a NodeList to an Array, as evergreen browser's implementation of forEach can iterater over a NodeList.

Also includes some other minor tweaks.

Testing Instructions

Code review @dgrammatiko @Fedik

[HLeithner]

This pull request has been automatically rebased to 5.2-dev.

[Fedik]

I have tested this item :white_check_mark: successfully on 0a28f6e5e78cedd95b2d6021cacbab3e14789113

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[viocassel]

I have tested this item :white_check_mark: successfully on 0a28f6e5e78cedd95b2d6021cacbab3e14789113

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[alikon]

RTC

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[pe7er]

Thanks @C-Lodder !