Cleanup: replace Main ID's foreach functions by macros.

Am really no a big fan of using macros for that kind of things, but
meh... C solution to do that with functions (using callbacks) is
even worse. :(

Fix T59062: Keyframed node properties stay linked after shading network duplication.

There is no reason not to duplicate Actions too here, especially when
Materials' Actions are pretty much impossible to edit from current UI
(afaik, DopeSheet editor does not has any way to change them?).

Fix T61446: (second part) Some items in editor and mode selectors are not translatable.

That one is utterly ugly fix really, but unfortunately a proper one
would require some changes to our RNA (or more precisely, pyrna) code,
so that when we subscript a dynamically generated RNA collection, the
item is somehow duplicated (and probably 'assigned' to its py object?),
before the temp RNA array memory is freed...

Fix NodeTree types UI messages not being properly tagged for translation.

Probably fix first part of T61446.

Fix T61515: Crash when unloading a scene with pynodes and idprop of type id.

Usual legacy/history crap in NodeTree code... Datablocks's specific
freeing code should never, ever do refcounting management, this is
handled by higher-level code from BKE_library area.

Fix T61506: Wrong user counting with ID properties in pynodes.

Nuke away old nodeCopyNode(), much better to use new BKE_node_copy_ex(),
which behaves as expected for the various optional flags that can be passed.

This also removes the need to handle ID refcounting in calling code
(ugly!) and allows us to remove an even uglier name from our codebase! :D

Note that this fixes three related issues actually, that bug was also
affecting copy/paste of nodes, and 'Separate with copy' operator (the
latter being actually fully wrong, since it was not refcounting
anything, not even node->id pointer...).

Cleanup: do not cleanup runtime data twice during ID copying...

More or less same code was being executed twice during ID copying.

Makes no sense to add yet another switch-by-ID-type to handle
specificaly runtime data during ID copying, we already have
BKE_xxx_copy_data() functions for that.

I18N Messages: fix confusion with Light meanings.

Using ID_LIGHT or ID_ID for "Lamp" meaning, "Light" without context
being for 'not heavy'.

That rename of data-block was not really nice on that side of things :/

Related to T43295.

Cleanup: rename `BLT_I18NCONTEXT_ID_LAMP` -> `BLT_I18NCONTEXT_ID_LIGHT`.

Fix T51771: UI Messages: Reserve 'Normal' to its geometric meaning.

Using 'Regular' instead for the common meaning, this avoids having to
add some i18n context disambiguation...