PY-11932 Put nulls for unresolved class types in MRO

Some of the ancestor class-like types may be unresolved. The best we
can do is to put nulls for all the unresolved classes to appropriate
places inside the MRO chain. What we used to do in this case it return
the empty sequence of the ancestors.
Fall back to old-style ancestors if C3 MRO fails and there are unresolved ancestors (PY-11401)

If the C3 MRO algorithm fails and the old-style ancestors algorithm
tells that there are unresolved ancestors, we return a single 'null'
ancestor as a sign that we don't know who the ancestors really are.

If there are no unresolved ancestors, then we fall back to the
old-style ancestors algorithm in order to make resolve work. A future
inspection for detecting incorrect MRO may warn the user about this
situation.
If mro() is overridden in metaclass, use normal MRO + unresolved ancestor (PY-11401)

We cannot evaluate the result of an overridden mro() method, so we
don't know the actual MRO chain. Let's assume that MRO is almost the
same as without this override and add an element of uncertainty by
appending a fake unresolved ancestor type to the MRO chain. Doing so
results in, for example, the unresolved references inspection ignoring
unresolved references for such a class.
reverted 'tests: platform prefix for light CodeInsight tests'
IDEA-CR-1100 move RequestBuilder to top level
IDEA-CR-1100 rename to productNameAsUserAgent
don't infer that simple getters are pure: currently it provides no value for the user
perform commit command with hgRepository instance as argument instead of VF

* tests fixed
* unnecessary checks removed
preserve folding model consistency on document change - remove fold regions which become equal
vfs: consistency checks on file operations
IDEA-CR-1106 don't include headers to error message by default
simplify
don't lowercase tags in html
#WEB-14679 fixed
fixed incorrect slots mapping (double and long slots were not checked in parameters)
[vcs] Deprecate unused setter (later will make the field immutable)
[vcs] IDEA-117448 Don't read & store patch text until really needed

ShelvedChangeList doesn't need patch text itself to provide the changes,
this texts are loaded and parsed in ShelvedChange#getChanges when needed

=> let read patch files in "ignore content" mode & use this mode
when ShelveChangeLists are loaded.
IDEA-126296, IDEA-130425 incorrect scrolling on undo/redo
EA-63550: fix IAE in JBListTable row animation when animated row is deleted
java 8 javadoc tags @apiNote, @implNote, @implSpec
quick javadoc: include new javadoc tags in view (IDEA-128304)