Use `u32` for sizes

[mnemonikr]

Should revisit the decision to use usize for various sizes that are defined as u32 within Ghidra's libsla. This includes VarnodeData

symbolic-pcode/crates/sla/src/ffi/sys.rs

Line 252 in 1019c0d

fn getSize(data: &VarnodeData) -> u32;

vs

symbolic-pcode/crates/sla/src/sleigh.rs

Line 116 in 1019c0d

pub size: usize,

and AddressSpace sizes:

symbolic-pcode/crates/sla/src/ffi/sys.rs

Lines 236 to 239 in 1019c0d

	#[rust_name = "word_size"]
	fn getWordSize(self: &AddrSpace) -> u32;
	#[rust_name = "address_size"]
	fn getAddrSize(self: &AddrSpace) -> u32;

vs

symbolic-pcode/crates/sla/src/sleigh.rs

Lines 186 to 187 in 1019c0d

	pub word_size: usize,
	pub address_size: usize,