Error Prone 2.21.0

New Checkers:

• AttemptedNegativeZero: Prevents accidental use of -0, which is the same as 0. The floating-point negative zero is -0.0.
• ICCProfileGetInstance: Warns on uses of ICC_Profile.getInstance(String), due to JDK-8191622.
• MutableGuiceModule: Fields in Guice modules should be final.
• NullableOptional: Discourages @Nullable-annotated Optionals.
• OverridingMethodInconsistentArgumentNamesChecker: Arguments of overriding method are inconsistent with overridden method.

Fixed issues: #3976, #3986, #4001, #4002, #4026, #4027

Full Changelog: v2.20.0...v2.21.0