[needs-docs][processing] Monkey patch stable external Processing API into qgis.processing

Instead of encouraging use of the internal Processing modules
(e.g. from processing.tools.general import run , import processing, ...)
instead expose all Python specific STABLE processing additions
to the qgis.processing module.

Instead, scripts and plugins should now use

from qgis.processing import run, algorithmHelp,...

This makes a clear distinction between internal Processing python
modules (i.e., everything else!) and the parts of Processing
which are stable and designed to be used by plugins and scripts.

TODO: QGIS 4.0 -- move the internal Processing plugin modules
to __processing, to clearer indicate that this is all internal
stuff.

Author: nyalldawson

python/plugins/processing/__init__.py

@@ -31,6 +31,17 @@
 from processing.tools.raster import *               # NOQA
 from processing.tools.system import *               # NOQA
 
+# monkey patch Python specific Processing API into stable qgis.processing module
+import qgis.processing
+qgis.processing.algorithmHelp = algorithmHelp
+qgis.processing.run = run
+qgis.processing.runAndLoadResults = runAndLoadResults
+qgis.processing.createAlgorithmDialog = createAlgorithmDialog
+qgis.processing.execAlgorithmDialog = execAlgorithmDialog
+qgis.processing.createContext = createContext
+qgis.processing.isWindows = isWindows
+qgis.processing.isMac = isMac
+
 
 def classFactory(iface):
     from processing.ProcessingPlugin import ProcessingPlugin