Revisit log4j2 Message.getFormat() deprecation for v9 #6377

Log4j 2.24.0 deprecated org.apache.logging.log4j.message.Message.getFormat(), and sentry-log4j2 still calls it to get the unformatted message template. The deprecation warning is suppressed in #5435 (log4j2 2.20.0 → 2.26.1) to keep the build passing under -Xlint:all -Werror.

• Call sites: SentryAppender.captureLog (populates the sentry.message.template log attribute) and SentryAppender.createEvent (sets Message.message on events) in sentry-log4j2/src/main/java/io/sentry/log4j2/SentryAppender.java.
• The deprecation note points to MultiformatMessage for implementing messages. It does not offer a replacement for reading a message's template, and getFormattedMessage() drops the template.
• In 2.26.1 the interface method is a default that returns null. Concrete classes such as ParameterizedMessage, ReusableParameterizedMessage, StringFormattedMessage, MessageFormatMessage and SimpleMessage still override it without a deprecation.
• Log4j 3 has only reached 3.0.0-beta3; no stable 3.0 is listed in the Apache release catalog.

Proposed by Nelson Osacky: suppress the warning now and revisit the call in the next major.

Action taken on behalf of Nelson Osacky.