Add assembly identity Api Check

[Anipik]

Assembly Identity rules

• assemblies should be not null
• names must be exactly same
• cultures must be same
• version of the right should be >= left (rightVersion == leftVersion under strict mode)
• Non strict mode
  leftKeyTokenNull or retargetable flag set => always true
  else leftKeyTokenNull == rightKeyTokenNull
• same rules for right under strict mode

added tests for each of these cases in strict and non-strict mode.

[ghost]

I couldn't figure out the best area label to add to this PR. If you have write-permissions please help me learn by adding exactly one area label.

[safern]

For these tests we are not asserting the messages because they are localized. Instead do a contains: AssemblyA and COntaines `AssemblyB'.

You can look at the other tests, but there is a CompatDifferenceComparer that doesn't compare the message. In order to assert the other properties of the difference.

Also, shouldn't this diagnostic ID be CP0004?

[Anipik]

CP0004 is thrown when mapper doesnot find the exact assembly and set one of the inputs as null

[safern]

A right. Should this have it's own diagnostic as well? Or you don't think it is worth it?

[Anipik]

I dont think its worth it. I am expecting the mapper scenario to be more common and we will hit that and version, culture and token are more interesting scenrios here.

[safern]

LGTM