Dropping codepoint for a glyph already in ufo1 included by codepoint & excluded by name

[RickyDaMa]

This looks really contrived, but I happened across it trying to implement exclude_glyphs for gftools' add-ds-subsets: googlefonts/gftools#1020. In the real world, the list of codepoints is typically far longer.

Reproducing snippet:

def test_repro(helpers):
    ufo1 = helpers.create_ufo(["A", "B"])
    b1 = ufo1["B"]
    b1.height = 100
    b1.unicodes = [0x42]

    ufo2 = helpers.create_ufo(["B", "C"])
    b2 = ufo2["B"]
    b2.height = 200
    b2.unicodes = [0x42]

    merge_ufos(
        ufo1,
        ufo2,
        exclude_glyphs=["B"],
        codepoints=[0x42],
    )

    assert "B" in ufo1
    assert ufo1["B"].height == 100
    assert ufo1["B"].unicode == 0x42  # fails

Expectation: /B retains its codepoint