Aliases don't work properly with TextUnmarshaler

[WGH-]

Given

testStructAB_TextUnmarshaler struct {
	A simpleTextUnmarshaler
	B simpleTextUnmarshaler
}

YAML document

a: &foo hello world
b: *foo

Incorrectly decodes to

a:
    value: hello world
b:
    value: ""

But the correct value is

a:
    value: hello world
b:
    value: hello world

This is a problem as of current main (cc10f15) and v4.0.0-rc.4.