[improve][meta] Upgrade Oxia client to 0.8.0 - #25964

Motivation

• Backport [improve][meta] Upgrade Oxia client to 0.8.0 #25962 to branch-4.2.
• Keep the Oxia client on 0.8.0 while leaving oxia-testcontainers at 0.7.4 because 0.8.0 is not published for that artifact.

Modifications

• Updated the Maven Oxia client version to 0.8.0 and split oxia-testcontainers to its own 0.7.4 property.
• Updated binary LICENSE entries for the Oxia 0.8.0 jars.
• Adjusted the Oxia config-file test reflection to read clientConfig from SessionManager.

Testing

• mvn -pl pulsar-metadata -DskipTests dependency:tree -Dincludes=io.github.oxia-db,dev.failsafe
• mvn -pl pulsar-metadata -am -Pcore-modules,-main -DskipTests -Dlicense.skip=true -Drat.skip=true -Dcheckstyle.skip=true -ntp package
• mvn -pl pulsar-metadata -am -Pcore-modules,-main -Dtest=MetadataStoreTest#testOxiaLoadConfigFromFile -DfailIfNoTests=false -Dsurefire.failIfNoSpecifiedTests=false -Dlicense.skip=true -Drat.skip=true -Dcheckstyle.skip=true -ntp test

Note: the targeted TestNG selector completed successfully but reported Tests run: 0, so the effective local validation is the reactor package/test-compile plus dependency and license-entry checks.