format-patch: learn --[no-]range-diff-notes

git-format-patch(1) passes on the notes behavior that it is using for
the patches to git-range-diff(1). In turn you get the same Git notes
displayed in the range diff as the ones you used to generate the
patches. And that makes sense in most cases.

However, I often make notes between series versions that mostly prepend
to the original. They end up looking like this:

    v3:
    [desc.]
    v2:
    [descr.]
    v1:
    [descr.]

These notes are meant for the git-format-patch(1) output since they
document the iterations. But including them also includes them in the
range diff. And they have nothing useful to say there.

Let’s teach git-format-patch(1) `--[no-]range-diff-notes` so that we
can pass in different notes refs to the range diff, or just turn them
off entirely.

In addition to storing the list of notes, we also need a boolean
`override` to distinguish these two cases:

1. No such options were given and empty list (use `--notes`)
2. Options were given and empty list (`--no-...` given; don’t use notes)

Unlike `--creation-factor`, `--[no-]range-diff-notes` does not error out
when used without `--range-diff`. This flexibility accommodates
workflows where users might configure default options in aliases or
wrapper scripts, allowing `--range-diff` to be toggled independently.

Add two tests here for the single-patch case, i.e. the case where the
range diff is on the patch and not in the cover letter. These are meant
as regression tests based on my encounter with single-patch range diff
notes handling bug.[1]

† 1: 155986b4 (format-patch: handle range-diff on notes correctly for
     single patches, 2025-09-25)

Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Kristoffer Haugsbakk <code@khaugsbakk.name>
Signed-off-by: Junio C Hamano <gitster@pobox.com>