[446252] Issue with feature ordering when merging FeatureMaps

In the case of equivalent ReferenceChange and FeatureMapChanges, the
FeatureMapChanges will take precedence when merging. This ensures that
the order of references inside the feature map is correctly maintained. 

The commit includes a new test case for the issue and updates the
existing test cases reaching the affected code.

Bug: 446252
Change-Id: I1bd13aadbd8e43c055a424329a5e70c8e47baca4
Signed-off-by: Alexandra Buzila <alexandra.buzila@gmail.com>