Adding the ability to use the global value for character count in newsfeeds

[Bakual]

Summary of Changes

Removes the default value from the feed_character_count parameter in newsfeed form and menu item.
Adds the "Show Global Value" feature to those two fields
This allows to leave the field empty and thus use the value from the component configuration.

Testing Instructions

1. Create a newsfeed
2. Create a menu item for that newsfeed
3. Play around with the "Characters Count" parameter and make sure it works as expected. If the field is empty, it should show a hint with the value from the component configuration.

Documentation Changes Required

None

[andrepereiradasilva]

works on news feed edit and news feed menu item type, but not working properly in "List All News Feed Categories" and "List News Feeds in a Category" menu item types

[Bakual]

I have no clue why I missed those two. Done now. 👍

[andrepereiradasilva]

I have tested this item ✅ successfully on 622b55e

works as described

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/12869.}

[brianteeman]

I have tested this item ✅ successfully on 622b55e

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/12869.}

[andrepereiradasilva]

RTC?

[brianteeman]

I am sure tobias will do that when he gets online (I shouldnt do it as I was a tester - but i sometimes forget that rule)

[andrepereiradasilva]

sure, just pinging in case someone forgot

[brianteeman]

I know that @zero-24 and I both run the Two Tests check on the issue tracker multiple times a day - we dont need to be pinged unless its been a few days in which case we have missed it

[andrepereiradasilva]

ok ok