Liboverride: Add more missing ID RNA pointers as overridable.

Fix T68789: Do not use new python format strings thingy in UI code.

This is 100% incompatible with translation...

Merge branch 'master' into asset-engine

Conflicts:
source/blender/blenkernel/intern/library.c

LibOverride: add some more missing override flags for RNA ID pointers.

Fix crash when loading a file with existing proxy, and lib has been edited.

Editing a lib char should never, ever be done once you have proxies of
it in your project, that will most certainly break a lot of things...

But at leats let's try no to crash here.

Fix T68806: UI: underscores instead of spaces in some labels.

LibOverride: Fix some more broken characters after override.

Think pretty much any ID pointer property should be overrideable
actually, without this reconstructing a local hierarchy of overriding
data-blocks simply cannot work properly...

LibOverride: do not allow diffing on collections' `all_objects` member.

This is useless (as diffing on `objects` + `children` shall be enough),
and potentially very time consuming in case of heavy hierarchy of
collections.

Cleanup: proper use of UNUSED_VARS_NDEBUG instead of random hack.

Fix T68651: LibOverride: Fix bad handling of RNA collections pointers.

We were storing the 'item' part in the RNA path of the override op
itself, which will not work with IDs because overriding local one might
not have the same name as the linked one (when some local ID with same
name already exists).

Now we are properly handling this using the expected actual override
operation, which stores necessary data (names or indices) from both
local and linked data.