Previously, when no file annotations were present, the FIR element
didn't have a source.
By making it nullable, it will only be created when appropriate and the
source will never be null.
#KT-55835
We can avoid body resolution in some cases because it is more
than out contract is required
So ANNOTATIONS_ARGUMENTS_MAPPING should be enough for all
non-body parts of a declaration to return fully-resolved FirElement
Body parts incudes: body and default values
^KT-59266 Fixed
In case of broken code e.g., duplicated classes provider would return first class,
though we definitely need some code insight in this case
at least to add navigation fixes, etc.
Similar to this, a file copy is created during completion,
where additional elements might appear and we need to search for them.
Added test cases for duplicated classes.
ensure fir annotations are included in FirDanglingModifierList and resolved,
dedicated DanglingTopLevelModifierListStructureElement exists for top
level lists only, class level lists are processed by containing structure
element
Kirill Rakhman