Allow noindex option in addition to no-link

[hojalot]

The Sphinx renderer maps the "no-link" option to "noindex" but a warning is generated since "noindex" is not in option_specs.

Add "noindex" where "no-link" is allowed.

[BrennanGit]

We've just upgraded our breathe to the new version (thanks @AA-Turner for getting it released).

The PR #959 has introduced a change which means ALL our directives get a toc/index entry now.

An example that shows the change follows:

.. tab:: C API

    .. doxygenfunction:: adsp_volume_control

    .. doxygenfunction:: adsp_volume_control_set_gain

    .. doxygenfunction:: adsp_volume_control_mute

    .. doxygenfunction:: adsp_volume_control_unmute

.. tab:: Python API

    .. autoclass:: audio_dsp.dsp.signal_chain.volume_control
        :noindex:

        .. automethod:: process
            :noindex:

        .. automethod:: set_gain
            :noindex:

        .. automethod:: mute
            :noindex:

        .. automethod:: unmute
            :noindex:

In version v4.35 this makes a contents like:

And in v4.36:

We'd like this to be configurable and it seems this PR might be half of the story (which is why I'm commenting here to keep discussion in one place).

Adding :no-link: is certainly an option to get :noindex: behaviour but then we lose the cross-referencing links which are pretty important to us.

I think adding the :noindex: option to all the directives and then gating the block added in #959 will give the desired behaviour but I'm not super familiar with breathe. I'm guessing a change like this would require some documentation changes (and maybe tests too).

I'm happy to create a PR with these changes or we can build on this one if @hojalot is amenable.

[hojalot]

@BrennanGit I'm fine with additions to this branch, or feel free to incorporate the change into another branch/PR. My intention was just to silence a warning so any more general work beyond that seems like a good thing!

[cmarqu]

Suggested change

	"noindex": flag,
	"noindex": flag,
	"no-index": flag,

Newer Sphinx releases support the syntax with - (it actually has become the default but without deprecating the original spelling).

[cmarqu]

Suggested change

	"noindex": flag,
	"noindex": flag,
	"no-index": flag,

Newer Sphinx releases support the syntax with - (it actually has become the default but without deprecating the original spelling).