The Rust extractor gated every non-function item on struct_item,
enum_item and trait_item, so tree-sitter-rust's static_item and
const_item never produced a node: a constant existed in the graph only
through the files that referenced it, never from the Rust that defines
it (0 of 783 names in a jdx/mise snapshot).
Add a branch for both node types: a module-level declaration gets a
node with a file-level contains edge, an associated const inside an
impl is attributed to the impl like a method, and the declared type is
referenced the way a struct field type is.
Fixes#3471
(cherry picked from commit 70ff464064)
L4XB
ab80fa7413