AVRO-3304: Drop-in reload4j to mitigate log4j 1.x

[RyanSkraba]

This is an alternative to #1458

That PR replaces the logging behind slf4j from log4j 1.x to slf4j-simple, while this PR drops in the reload4j replacement.

Both these solutions are "mitigation" solutions for current CVEs, while downstream projects still bring in log4j 1.x dependencies.

I've verified that the classes in the generated avro-tools uberjar are the reload4j replacements.

Jira

• My PR addresses the following Avro Jira issues and references them in the PR title. For example, "AVRO-1234: My Avro PR"
  • https://issues.apache.org/jira/browse/AVRO-3304
  • In case you are adding a dependency, check if the license complies with the ASF 3rd Party License Policy.

Tests

• My PR does not need testing for this extremely good reason: the equivalent of a version bump.

Commits

• My commits all reference Jira issues in their subject lines. In addition, my commits follow the guidelines from "How to write a good git commit message":
  1. Subject is separated from body by a blank line
  2. Subject is limited to 50 characters (not including Jira issue reference)
  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

Documentation

• In case of new functionality, my PR adds documentation that describes how to use it.
  • All the public functions and the classes in the PR contain Javadoc that explain what it does

[martin-g]

A new version of Reload4j is coming: https://twitter.com/ceki/status/1483710574051696641

[martin-g]

Merged!
We can easily update the version of Reload4j once it is released!

[pjfanning]

Can I ask what happens if Avro and its reload4j dependency is used with Hadoop an/or Spark that still have log4j(v1) dependencies? Presumably, you will just end up with 2 separate jar files and the classloader will randomly choose the classes from reload4j or log4g(v1) jars. It's possible that I've misinterpreted how the reload4j change will work in practice.

[martin-g]

Hi @pjfanning !
We have updated avro**-tools** to exclude the transitive dependency to log4j 1.x and added a dependency to reload4j. So log4j could be in the classpath only if you add it by other means in your application build configuration, or if it comes as a transitive dependency of another dependency.
But yes, if you have both in the classpath then a random one will be chosen.