refactor(zscript): use faster register allocation in jit

asmjit's register allocation was using a bin-packing algorithm. This
turns out to be very slow for the assembly that our jit compiler emits,
since the vast majority of variables exist for only a single basic
block. Instead of bin-packing, the much faster and simpler linear scan
register allocation algorithm is now used.

For a very large 200k-instruction script, compilation went from 19.5s to
2.8s (a 85% decrease).

With this improvement, the 20k-instruction limit for jit has been
removed. One example of the impact of this is that `yuurand.zplay`,
which the jit compiler was previously mostly disabled for since most of
its scripts are huge, now has all its scripts compiled. This increased
the average FPS for `yuurand.zplay` from ~320 to ~2000, while still
reducing the total time spent compiling.

Theoretically this change in register allocation may produce slower
runtime code, but there was no drop in FPS realized in the `maths.zs`
stress test.

CMakeLists.txt

@@ -719,9 +719,9 @@ elseif(JIT_BACKEND STREQUAL "x64")
 	FetchContent_Declare(
 		asmjit
 		GIT_REPOSITORY
-			https://github.com/asmjit/asmjit.git
+			https://github.com/connorjclark/asmjit.git
 		GIT_TAG
-			bfa0bf690c2e90cc0844f2f012efa41b916bde7e
+			6d153ad8e13984841c2c642c0fa11e60f41e54dc
 	)
 	FetchContent_MakeAvailable(asmjit)
 	target_link_libraries(zplayer PRIVATE asmjit)

src/zc/jit_x64.cpp

@@ -615,16 +615,6 @@ JittedFunction jit_compile_script(script_data *script)
 
 	al_trace("[jit] compiling script type: %s index: %d size: %zu name: %s\n", ScriptTypeToString(script->id.type), script->id.index, size, script->meta.script_name.c_str());
 
-	// Check if script is like, really big.
-	// Anything over 20,000 takes ~5s, which is an unacceptable delay. Until scripts can be compiled w/o pausing execution of the engine,
-	// or a way to speed up compilation is found, set a hard limit on script size.
-	size_t limit = 20000;
-	if (!is_ci() && size >= limit)
-	{
-		al_trace("[jit] script type %s index %d too large to compile quickly, skipping\n", ScriptTypeToString(script->id.type), script->id.index);
-		return nullptr;
-	}
-
 	std::optional<ScriptDebugHandle> debug_handle_ = std::nullopt;
 	if (DEBUG_JIT_PRINT_ASM)
 	{