[com_associations] Creating missing filters

[infograf768]

This PR allows filtering items (articles, contacts, newsfeeds) per category.
It also allows to filter categories (for articles, contacts, newsfeeds) per level.
It also allows filtering menu items per level

Testing instructions

Create a multingual site with associations. 2 languages are enough.

Create articles, contacts, newsfeeds tagged to one language (it's enough for the test but one can test with both languages.)
Create categories and sub-categories for each component above tagged to one language (it's enough for the test but one can test with both languages.)
Create menu items and sub-menu items tagged to one language (it's enough for the test but one can test with both languages.)

Display Associations list:
/administrator/index.php?option=com_associations&view=associations

Before patch, there is no filtering of the items above by category.
Before patch there is no filtering by level for categories or menu items.

After patch these are now available.
Test everything is fine.

For categories

For Menu items

For items

Note: this PR does not solve yet the sorting by category.

@rdeutz

[brianteeman]

I have tested this item ✅ successfully on 1763507

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[alikon]

I have tested this item ✅ successfully on 1763507

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[ghost]

RTC as there are 2 successfully Tests?

[infograf768]

RTC. Thanks for testing!

@rdeutz will be confirming on Friday

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