Instead of storing a u32 index into a cache vector and looking up the
cache at runtime through a chain of dependent loads (load Executable*,
load vector data pointer, multiply index, add), store the actual cache
pointer as a u64 directly in the instruction stream.
A fixup pass (Executable::fixup_cache_pointers()) runs after Executable
construction in both the Rust and C++ pipelines, walking the bytecode
and replacing each index with the corresponding pointer.
The cache pointer type is encoded in Bytecode.def (e.g.
PropertyLookupCache*, GlobalVariableCache*) so the fixup switch is
auto-generated by the Python Op code generator, making it impossible
to forget updating the fixup when adding new cached instructions.
This eliminates 3-4 dependent loads on every inline cache access in
both the C++ interpreter and the assembly interpreter.
Move the Bytecode.def parser, field type info, and layout computation
out of Rust/build.rs into a standalone BytecodeDef crate. This allows
both the Rust bytecode codegen (build.rs) and the upcoming AsmIntGen
tool to share a single source of truth for instruction field offsets
and sizes.
The AsmIntGen directory is excluded from the workspace since it has
its own Cargo.toml and is built separately by CMake.
