options: drop --opt:subopt option names

For all suboptions, "flat" options were available by separating the
parent option and the sub option with ":", e.g. "--rawvideo:w=123". Drop
this syntax and use "-" as separator. This means even suboptions are
available as normal options now, e.g. "--rawvideo-w=123". The old syntax
doesn't work anymore.

Note that this is completely separate from actual suboptions. For
example, "-rawvideo w=123:h=123" still works. (Not that this syntax is
worth supporting, but it's needed anyway, for for other things like vf
and vo suboptions.)

As a consequence of this change, we also have to add new "no-" prefixed
options for flag suboptions, so that "--no-input-default-bindings"
works. ("--input-no-default-bindings" also works as a consequence of
allowing "-input no-default-bindings" - they are handled by the same
underlying option.)

For --input, always use the full syntax in the manpage. There exist
suboptions other than --input (like --tv, --rawvideo, etc.), but since
they might be handled differently in the future, don't touch these yet.

M_OPT_PREFIXED becomes the default, so remove it. As a minor unrelated
cleanup, get rid of M_OPT_MERGE too and use the OPT_SUBSTRUCT() macro in
some places.

Unrelated: remove the duplicated --tv:buffersize option, fix a typo in
changes.rst.
options: fix --no-shuffle and --no-{

--no-shuffle accidentally did nothing after commit 57879a2. The options
--no-{ and --no-} make no sense and shouldn't exist (wrong option type).
demux_rawvideo: remove ancient video dimension presets

I can't see much value in them. Just specify the size manually.
vf_stereo3d: get rid of m_obj_presets_t usage

The code becomes amazingly simpler.
vf_scale: remove video dimension presets ("presize" suboption)

This wasn't really useful, and the option preset mechanism is awfully
complex.
m_option: remove preset mechanism

Was very complicated to use, and its uses have been removed in the
previous commits.

(While this feature sounded kind of useful, it could be rewritten in
a much simpler way, like storing presets as strings, and then using
the option parser to apply a preset. The removed code did some major
pointer juggling to handle raw values, which made it hard to use.)
vf_yadif: switch to option parser, allow disabling by default

Use the option parser instead of sscanf. Remove the parameter changing
the field dominance (it has been marked deprecated for ages). Add a new
suboption "enabled", which can be used to disable the filter by default,
until it's enabled at runtime:

    mpv -vf yadif=enabled=no