in QgsMapSettings to restrict where labels are allowed to be placed
within.
If set, this overrides the default behavior of allowing labels to
be placed anywhere inside the rendered map extent.
And replace labeling engine dialog "Draw text as outlines" checkbox with a combobox
presenting the choice of always rendering as outlines OR text.
(This will allow us to easily add additional methods in future, e.g. potentially
a "Render as text wherever possible" setting, for defaulting to text objects
whenever it doesn't impact the rendering quality to do so)
The new QgsRenderContext::TextRenderFormat enum controls how text
should be handled during a render operation, e.g. whether to render
text as outlines (paths) or keep it as real text objects.
Deprecate previous arguments in QgsTextRenderer which handled
this same use case.
This allows us to make the setting vary per-render, instead of
having a single global flag controlling the setting. Ultimately
this will allow us to have different behaviour within the
canvas renders vs print layout exports.
Refs #3975
