fix: resolve bitfield accessor name conflicts

[zRedShift]

Summary

Fixes #3322

When a struct has bitfields like x and set_x, the generated getter for set_x collides with the generated setter for x (both named set_x), producing duplicate method definitions that fail to compile.

Root cause

Bitfield accessor name dedup only checked against C++ methods (has_method), not against other bitfield accessors, and codegen's method/constructor/destructor emission had no knowledge of bitfield accessor names at all. This left several collision classes unhandled:

• Two bitfields whose accessor names overlap (x + set_x)
• Overloaded C++ methods whose numbered Rust names (foo1) collide with a bitfield
• Destructors (destruct) and constructors (new, new1) colliding with bitfields
• _raw accessor variant collisions (set_x_raw vs bitfield set_x_raw)
• Rust keyword mangling (type → type_) not considered during method dedup

Fix

IR phase (comp.rs): resolve inter-bitfield accessor collisions by tracking all assigned names (getter, setter, and _raw variants) and suffixing with _bindgen_bitfield until unique. Handles chains like x / set_x / set_x_bindgen_bitfield.

Codegen phase (mod.rs): seed the method_names set with bitfield accessor names before emitting C++ methods, constructors, and destructors. The existing method dedup mechanism then renames colliding wrappers instead of producing duplicates. Method names are Rust-mangled before dedup so keyword collisions (e.g. C++ type → Rust type_) are caught.

The behavior change: bitfield accessors keep their natural names, and colliding C++ method/ctor/dtor wrappers get numeric suffixes (type_1, destruct1, etc.).