Fix allowedit for field group, only use component ACL if group ID is zero (new record)

[ggppdk]

Same fix as fix that had been applied here in the past to the article controller :

https://github.com/joomla/joomla-cms/blob/staging/administrator/components/com_content/controllers/article.php#L80-L89

https://github.com/joomla/joomla-cms/blob/staging/administrator/components/com_content/controllers/article.php#L112

Same as PRs
#17838
#17839

This is minor security issue,
if user than has "edit" on fields component, is denied editing configuration of a specific field group,
then user will still be able to edit the field group's configuration

Summary of Changes

Testing Instructions

Expected result

Actual result

Documentation Changes Required

[sanderpotjer]

I have tested this item ✅ successfully on 4ee0e26

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/17840.}

[Sieger66]

I have tested this item ✅ successfully on 4ee0e26

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/17840.}

[ghost]

RTC after two successful tests.