TreeTraversingParser and UTF8StreamJsonParser create contexts differently

[apetrelli]

UTF8StreamJsonParser creates a child context every time:

• it encounters a property
• if the property is collection-like a new context is born for every element in the collection.

TreeTraversingParser instead creates a child context every time a new object has been created.
The result is that, for collection-like properties, the current value of the current context is first set with the container object, then with the collection itself.

I attach a small test case with two tests in which I created a DeserializerModifier to try to append a parent to all children objects.
jackson-bug-test.zip
I tried with versions 2.9.5 and 2.8.10.

[cowtowncoder]

Possibly dup of #1803? (or just related)

[apetrelli]

@cowtowncoder no, that issue refers to the passing of parent context externally, instead this issue is about the creation of subcontexts, that in UTF88StreamJsonParser happens more frequently than in TreeTraversingParser.

[cowtowncoder]

Good news -- finally found time to go back to this, and filed separate #2525 to resolve slightly bigger issue (there is also TokenBuffer to consider).
Provided test now passes: fix will be in 2.11.0, eventually: I am hesitant to make a change in patch for 2.10 (although it is relatively early) just because there is non-trivial chance of some code somewhere relying on some aspects of old handling.