Enforce correct type-use annotation locations for nested types

[armughan11]

Enforce correct type-use annotation locations for nested types as per JSpecify norms. We enforce type-use annotations to be on the inner class and raise an error if they are not. For annotations that are both type use and declaration, we raise an error at an invalid location.

Current behavior

// All three are ok

@Nullable A.B.C foo1 = null;
A.@Nullable B.C foo2 = null;
A.B.@Nullable C foo3 = null;

New behavior

// BUG: Diagnostic contains: Type-use nullability annotations should be applied on inner class
@Nullable A.B.C foo1 = null;
// BUG: Diagnostic contains: Type-use nullability annotations should be applied on inner class
A.@Nullable B.C foo2 = null;
A.B.@Nullable C foo3 = null;

For annotations which are both declaration and annotation and type-use, only foo2 throws an error since the location isn't apt for either scenarios

[codecov]

Codecov Report

Attention: Patch coverage is 90.62500% with 3 lines in your changes missing coverage. Please review.

Project coverage is 87.56%. Comparing base (940c40e) to head (61b0cdc).

Files with missing lines	Patch %	Lines
...away/src/main/java/com/uber/nullaway/NullAway.java	81.81%	1 Missing and 1 partial ⚠️
...c/main/java/com/uber/nullaway/NullabilityUtil.java	95.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #1045      +/-   ##
============================================
+ Coverage     87.54%   87.56%   +0.01%     
- Complexity     2138     2155      +17     
============================================
  Files            83       83              
  Lines          7003     7030      +27     
  Branches       1367     1376       +9     
============================================
+ Hits           6131     6156      +25     
- Misses          451      452       +1     
- Partials        421      422       +1     

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[msridhar]

This is a great start! I think we are missing checking on various occurrences of annotated types, like method return types. We should be doing checking in all the places that this checker does it. Can we add that, and also tests?

[msridhar]

I can't understand this check and why it occurs here? I think the check should occur independent of whether the initializer assignment is valid. If we need to possibly report multiple error messages from this method, we can use the state.reportMatch API to report the errors and then just always return Description.NO_MATCH.

[msridhar]

If these null checks are necessary the parameters should be @Nullable. But I don't think they are needed?