Fix ByteBuf leak in BaseTransactionalMap.isEqual() - #7303

Problem

BaseTransactionalMap.isEqual() encodes both arguments into ByteBuf objects, but its finally block calls readableBytes() on them instead of release():

private boolean isEqual(Object value, Object oldValue) {
    ByteBuf valueBuf = ((RedissonObject) map).encodeMapValue(value);
    ByteBuf oldValueBuf = ((RedissonObject) map).encodeMapValue(oldValue);
    try {
        return valueBuf.equals(oldValueBuf);
    } finally {
        valueBuf.readableBytes();
        oldValueBuf.readableBytes();
    }
}

readableBytes() only queries the buffer; it does not free it. So both encoded buffers leak on every isEqual() call. The sibling RedissonTransactionalBucket.isEquals() was already fixed in #7216, and BaseTransactionalSet.isEqual() already calls release().

Fix

Release both buffers in the finally block.

Test

Adds RedissonTransactionalMapTest#testContainsValueReleasesEncodedBuffers. It tracks ByteBuf instances allocated by a custom map-value encoder during transactional containsValue() (the path that calls isEqual() on local state) and asserts both buffers are released.

Executed:

• mvn -pl redisson -Punit-test -Dtest=RedissonTransactionalMapTest#testContainsValueReleasesEncodedBuffers test RED on master (refCnt 1), GREEN after the fix
• mvn -pl redisson -Punit-test -Dtest=RedissonTransactionalMapTest test 16/16
• mvn -pl redisson -Punit-test -Dtest=RedissonTransactionalMapCacheTest,RedissonTransactionalSetTest test 25/25

Fixes #7302