* Document how `JsonAdapter` creates adapter instances & add tests
* Extend `JsonAdapter.nullSafe()` documentation
* Improve test for JsonAdapter factory returning null
Existing test `JsonAdapterNullSafeTest` had misleading comments; while it
did in the end detect if null had not been handled correctly, that only
worked because the field `JsonAdapterFactory.recursiveCall` is static and
one test method therefore affected the state of the other test method.
If the test methods were run separately in different test runs, they would
not have detected if null was handled correctly, because the factory would
not have returned null.
* Extend JsonAdapter nullSafe test
* Extend test
* Adds a javadoc summary to the methods in the `SerializedName` annotation
Fixes the `MissingSummary` warn given by ErrorProne
* Adds a javadoc summary to the methods of the `ExclusionStrategy` annotation
Fixes the `MissingSummary` warn given by ErrorProne
* Adds a javadoc summary to `getDeclaringClass()` and `getName()` methods of the `FieldAttributes` class
Fixes the `MissingSummary` warn given by ErrorProne
* Adds a javadoc summary to `getMajorJavaVersion()` and `isJava9OrLater()` methods of the `JavaVersion` class
Fixes the `MissingSummary` warn given by ErrorProne
* Adds a comment in the empty catch block of the `AccessChecker:101` class
Fixes the `EmptyCatch` warn given by ErrorProne
* Adds a comment in the empty catch block of the `DefaultDateTypeAdapter:158` class
Fixes the `EmptyCatch` warn given by ErrorProne
* Adds a comment in the empty catch blocks of the `UnsafeAllocator:(67|92|113)` class
Fixes the `EmptyCatch` warn given by ErrorProne
* Adds a comment in the empty catch block of the `DateTypeAdapter:85` class
Fixes the `EmptyCatch` warn given by ErrorProne
* Fixes javadoc param of the `deserialize(...)` method of the `JsonDeserializer` interface
Fixes the `InvalidParam` warn given by ErrorProne
* Adds a charset `StandardCharsets.UTF_8` in the `resourceToString()` method of the `ParseBenchmark` class
Fixes the `DefaultCharset` warn given by ErrorProne
* Fixes a typo
* Implements review feedback
* Adds blank line before @ tag.
