Added support for Apache Validate

[Asapin]

Added support for Apache Validate: https://github.com/apache/commons-lang/blob/master/src/main/java/org/apache/commons/lang3/Validate.java

We recently started to use these Apache methods to validate some data but quickly found out that NullAway don't support them since they are not properly annotated. Here's a fix that adds support for these methods along with test cases for each method.

I noticed that Apache library generally has different validation methods for String, Map and Collection, but they all end up with the same signature when analyzed by NullAway (probably because these methods use generics).
Examples of such methods:

public static <T extends Collection<?>> T notEmpty(final T collection) {
}

public static <T extends Map<?, ?>> T notEmpty(final T map) {
}

public static <T extends CharSequence> T notEmpty(final T chars) {
}

But I decided to add a separate unit test for each of these methods in case NullAway will change how it generates method's signature in the future

[CLAassistant]

All committers have signed the CLA.

[msridhar]

@Asapin thanks for the contribution! Can you run ./gradlew googleJavaFormat locally to fix formatting and then push again?

[Asapin]

I tried to run ./gradlew googleJavaFormat locally, but my terminal (PowerShell) created 700+ processes, consumed 22 Gbs of RAM and crashed.
./gradlew.bat googleJavaFormat has the same effect.

And if I run googleJavaFormat task directly from IDEA's Gradle window, it finishes in 2 seconds with the message

> Task :googleJavaFormat FAILED

Detected Java syntax errors in the following files (you can exclude them from this task, see "https://github.com/sherter/google-java-format-gradle-plugin" for details):

and then it prints a list of seemingly all source files that exist in the project.

Is this expected behavior (I doubt, but who knows)? Could it be because I'm using Windows?

Update: tried to run this task in WSL Ubuntu. At first it complained that gradlew contained CRLF. But after fixing it (should I create a separate PR for that?) it again showed the same Task :googleJavaFormat FAILED message

[msridhar]

For now I just ran formatting on Mac and it works. @Asapin if you can please file an issue on GJF not working on Windows. We should probably fix by just switching to Spotless. I will try to review the change soon.

[lazaroclapp]

LGTM, and I appreciate the comprehensive test suite!