* To fix the Ruby 3.3.5 warnings:
  #1061
* concurrent-ruby only uses 7 constants from Logger, so just copy those over.

Niche case - when clearing class members for new definition,
avoid trying to remove members present on ancestor classes.

This patch forces rake-compiler to emit bytecode for Java 8 level
of JVM. rake-compiler currently defaults to Java 1.7 source and
target, but that version is no longer supported by recent JDKs
such as Java 21 (see rake-compiler/rake-compiler#242
for a patch to update rake-compiler).

This patch sets our minimum Java level to 8, bypassing the default
in rake-compiler and allowing builds on Java 21+.

Signed-off-by: Rui Chen <rui@chenrui.dev>