Vector type resolution/coercion fixes

[schmee]

Peer type resolution for vectors

This is consistent with how coercion for vectors work. So now you can do this:

var a: @Vector(2, u16) = .{1, 2};
var b: @Vector(2, u8) = .{2, 1};
const c = @min(a, b);

where previously you had to cast explicitly:

var a: @Vector(2, u16) = .{1, 2};
var b: @Vector(2, u8) = .{2, 1};
var c: @Vector(2, u16) = b;
const c = @min(a, c);

Fix result pointer coercion array -> vector

Previously this worked for array to vector where the element type matched exactly (e.g [4]u8 to @Vector(4, u8)) since that is performed with a simple .bitcast operation, but now it also works for types where the array is coercible to the vector type (e.g [4]u8 to @Vector(4, u16)).