cgen: fix assign optional aliases of fixed array (fix #23185)

[yuyi98]

This PR fix assign optional aliases of fixed array (fix #23185).

• Fix assign optional aliases of fixed array.
• Add test.

type Addr = [4]u8

fn main() {
	mut addr := ?Addr(none)
	addr = Addr([u8(1), 2, 3, 4]!)
	println(addr)
	assert '${addr}' == 'Option(Addr([1, 2, 3, 4]))'
}

PS D:\Test\v\tt1> v run .
Option(Addr([1, 2, 3, 4]))

_{Huly®: V_0.6-21625}

[spytheman]

Excellent work.