add i32 support and make it extensible

tests/failing_tests/vmlinux/i32_test.py

@@ -0,0 +1,23 @@
+from ctypes import c_int64, c_int32
+from pythonbpf import bpf, section, bpfglobal, compile_to_ir, compile
+from vmlinux import struct_xdp_md
+from vmlinux import XDP_PASS
+
+
+@bpf
+@section("xdp")
+def print_xdp_data(ctx: struct_xdp_md) -> c_int64:
+    data = ctx.data  # 32-bit field: packet start pointer
+    something = c_int32(2 + data)
+    print(f"ctx->data = {something}")
+    return c_int64(XDP_PASS)
+
+
+@bpf
+@bpfglobal
+def LICENSE() -> str:
+    return "GPL"
+
+
+compile_to_ir("i32_test.py", "i32_test.ll")
+compile()