Infer generics for assignments

[haewiful]

• Infer Nullability for assignments of instances with type parameters. ex) Foo<@Nullable Object> f = Foo.make(null);

• void genericInferenceOnAssignments() in GenericMethodTests.java

[msridhar]

@haewiful thanks for this! It looks like CI fails on the :nullaway:buildWithNullAway task:

https://github.com/uber/NullAway/actions/runs/12978381939/job/36192901792?pr=1131#step:5:606

I suggest looking at the code it is crashing on and trying to write a unit test that causes the same failure, which will make it easier to debug.

[codecov]

Codecov Report

Attention: Patch coverage is 88.00000% with 6 lines in your changes missing coverage. Please review.

Project coverage is 88.23%. Comparing base (f064222) to head (8a30816).

Files with missing lines	Patch %	Lines
...ava/com/uber/nullaway/generics/GenericsChecks.java	86.95%	0 Missing and 6 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #1131      +/-   ##
============================================
- Coverage     88.24%   88.23%   -0.01%     
- Complexity     2263     2275      +12     
============================================
  Files            85       85              
  Lines          7314     7361      +47     
  Branches       1458     1474      +16     
============================================
+ Hits           6454     6495      +41     
  Misses          432      432              
- Partials        428      434       +6     

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