Fix #9923 (broken arrow symbol)
Add convenience functions to Python test utilities for rendering with map settings

- Update labeling unit tests to use new functions
- All labeling test classes render separately from QgsRenderChecker
- Update labeling server test class to sync map settings to temp project
Add ability to define QImage format for render jobs via map settings

- Defaults to QImage::Format_ARGB32_Premultiplied, as before
- Update labeling unit tests to use defined format
Add labeling engine overrides to map settings

- Allows for setting engine options, without having to edit user's project settings
Update labeling unit tests to work with engine overrides in map settings
Note about PdfFormat and NativeFormat for QPrinter PDF output and embedding fonts

- Unlike the Qt issues for NativeFormat on Mac, choosing to print, then Save as PDF, embeds fonts
Initial fix for #3975, label engine vectorizing texts in SVG and PDF output

- Add labeling engine option to render text-as-text
- Default is still text-as-outlines (vectorized), due to differences between text (as text) and buffer (as outline) methods
- Good output with printing to PDF (searchable, selectable text and embedded fonts)
- OK output with SVG, but differences between text (as text) and buffer (as outline) methods

Does not yet include unit tests or auto-setting of text-as-text for SVG output