CppTools: Provide hints about chosen project part for editor document

Parse issues can have multiple reasons (invalid kit, not a project file,
actual parse issue) and we should be able to tell them apart. With this
change, we can distinguish between the fallback project part and a
ambiguous project part.

Follow up changes will use this to display more accurate diagnostics.

Change-Id: Icc8767607cc17dc14d6227b07f34e81ba5525a96
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/cpptools/cpptools.qbs

@@ -61,7 +61,6 @@ Project {
             "cppfunctionsfilter.cpp", "cppfunctionsfilter.h",
             "cppincludesfilter.cpp", "cppincludesfilter.h",
             "cppindexingsupport.cpp", "cppindexingsupport.h",
-            "cpplanguage.h",
             "cpplocalsymbols.cpp", "cpplocalsymbols.h",
             "cpplocatordata.cpp", "cpplocatordata.h",
             "cpplocatorfilter.cpp", "cpplocatorfilter.h",
@@ -81,6 +80,7 @@ Project {
             "cpptoolsbridgeqtcreatorimplementation.cpp", "cpptoolsbridgeqtcreatorimplementation.h",
             "cpptools.qrc",
             "cpptools_global.h",
+            "cpptools_utils.h",
             "cpptoolsconstants.h",
             "cpptoolsjsextension.cpp", "cpptoolsjsextension.h",
             "cpptoolsplugin.cpp", "cpptoolsplugin.h",