This change cleans up some methods in the CharArrays class from x-pack, which
includes the unification of char[] to utf8 and utf8 to char[] conversions that
intentionally do not use strings. There was previously an implementation in
x-pack and in the reloading of secure settings. The method from the reloading
of secure settings was adopted as it handled more scenarios related to the
backing byte and char buffers that were used to perform the conversions. The
cleaned up class is moved into libs/core to allow it to be used by requests
that will be migrated to the high level rest client.
Relates #32332
This is related to #28898. This PR implements pooling of bytes arrays
when reading from the wire in the http server transport. In order to do
this, we must integrate with netty reference counting. That manner in
which this PR implements this is making Pages in InboundChannelBuffer
reference counted. When we accessing the underlying page to pass to
netty, we retain the page. When netty releases its bytebuf, it releases
the underlying pages we have passed to it.