HBASE-30060: Add documentation about addressing multiple SLF4J bindings

[kgeisz]

https://issues.apache.org/jira/browse/HBASE-30060

This pull request adds some documentation for how to get around the Class path contains multiple SLF4J bindings warning you may see after starting HBase when you also have a local installation of Hadoop. Knowing what to do is important because Hadoop's SLF4J binder may end up getting used instead of HBase's. If this happens, then any log settings you have for HBase get overridden. For example, if you want to activate DEBUG logging for HBase, then you won't see that happen due to Hadoop's binding being used.

[Copilot]

Pull request overview

Adds troubleshooting documentation for resolving “Class path contains multiple SLF4J bindings” warnings when starting HBase in environments where a local Hadoop installation contributes conflicting SLF4J binders.

Changes:

• Document the cause and impact of multiple SLF4J bindings overriding HBase’s Log4j2 configuration.
• Provide a workaround via HBASE_DISABLE_HADOOP_CLASSPATH_LOOKUP=true in conf/hbase-env.sh.
• Include an example of the SLF4J multiple-bindings warning output.

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The SLF4J warning snippet is console output; elsewhere in this doc similar output blocks use an explicit language (e.g., text). Consider changing this fence to text for consistent rendering/syntax highlighting.

[Copilot]

This example output includes a specific contributor username/path (/Users/kgeiszler/...). To avoid embedding personal identifiers and to make the example more broadly applicable, consider replacing it with a placeholder like $HOME/.m2/... (and optionally eliding version numbers).

Suggested change

	SLF4J: Found binding in [jar:file:/Users/kgeiszler/.m2/repository/org/apache/logging/log4j/log4j-slf4j-impl/2.25.3/log4j-slf4j-impl-2.25.3.jar!/org/slf4j/impl/StaticLoggerBinder.class]
	SLF4J: Found binding in [jar:file:$HOME/.m2/repository/org/apache/logging/log4j/log4j-slf4j-impl/2.25.3/log4j-slf4j-impl-2.25.3.jar!/org/slf4j/impl/StaticLoggerBinder.class]