script: copy include! files from script_bindings to script's OUT_DIR (#36384)

copy generated `include!`d files from script_bindings's OUT_DIR, to
script's OUT_DIR to allow Rust Analyzer to load them.
This is done to bypass limitation of Rust Analyzer:
https://github.com/rust-lang/rust-analyzer/issues/17040

Also build script will now be rerun only when there are actual changes
to concrete bindings due to emitted `cargo::rerun-if-changed` (not for
each change in script crate).

Testing: It compiles so it works, I tested manually and RA now works as
expected (although we need to from type alias to concrete union-types
definitions)
Fixes:
https://servo.zulipchat.com/#narrow/channel/263398-general/topic/rust-analyzer.20failed.20to.20include.20codes.20in.20script_bindings

---------

Signed-off-by: sagudev <16504129+sagudev@users.noreply.github.com>

components/script_bindings/codegen/CodegenRust.py

@@ -8522,7 +8522,7 @@ class GlobalGenRoots():
         ]
         imports = CGList([CGGeneric(f"use {mod};") for mod in mods], "\n")
 
-        phf = CGGeneric("include!(concat!(env!(\"BINDINGS_OUT_DIR\"), \"/InterfaceObjectMapPhf.rs\"));")
+        phf = CGGeneric("include!(concat!(env!(\"OUT_DIR\"), \"/InterfaceObjectMapPhf.rs\"));")
 
         return CGList([
             CGGeneric(AUTOGENERATED_WARNING_COMMENT),