click event emitted 2 times from a single click in form field

[nit23uec]

Description

1. https://github.com/adobe/helix-rum-enhancer/blob/main/modules/index.js#L327
2. https://github.com/adobe/helix-rum-enhancer/blob/main/plugins/form.js#L45
   potential fix: in (2), honour optelhandled flag and return if its true.

To Reproduce
Steps to reproduce the behavior:

1. Go to 'https://www.similac.com/rewards.html'
2. Click on 'First Name'
3. Go to network tab
4. See 2 click events

Expected behavior
A single click event should be recorded for a single click
Screenshots
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Version:
run: $ hlx --version

Additional context
Add any other context about the problem here.