Upgraded librdkafka version to 1.9.2.

[javabrett]

Upgraded librdkafka version to 1.9.2.

Added OAUTHBEARER OIDC authentication example.

[androndo]

@javabrett please update librdkafka to new release 2.0.0 or 2.0.1.
Also thank you for PR, OIDC auth feature very helpful for me too.

[aviv-amdocs]

For any future explorer:
I built it with librd 2.8.0 using only this patch:

diff --git bootstrap.sh bootstrap.sh
index 6c04dd4..409c19a 100755
--- bootstrap.sh
+++ bootstrap.sh
@@ -11,7 +11,7 @@

 set -o errexit -o nounset -o pipefail

-: "${LIBRDKAFKA_VERSION:=v1.8.2}"
+: "${LIBRDKAFKA_VERSION:=v2.8.0}"

 lrk_install_deps="--install-deps"
 lrk_static="--enable-static"
@@ -163,7 +163,7 @@ export STATIC_LIB_jansson="$DEST/lib/libjansson.a"

 # libserdes does not have a pkg-config file to point out secondary dependencies
 # when linking statically.
-export LIBS="$(pkg_cfg_lib rdkafka) $(pkg_cfg_lib yajl) $STATIC_LIB_avro $STATIC_LIB_jansson -lcurl"
+export LIBS="$(pkg_cfg_lib rdkafka) $(pkg_cfg_lib yajl) $STATIC_LIB_avro $STATIC_LIB_jansson -lcurl -lz"

 # Remove tinycthread from libserdes b/c same code is also in librdkafka.
 ar dv $DEST/lib/libserdes.a tinycthread.o

and it seems to work fine.