Increase the io_uring completion queue size to resolve warnings and improve the plaintext test performance

```
io.netty.channel.uring.IoUringIoHandler processCompletionsAndHandleOverflow
vertx: WARNING: CompletionQueue overflow detected, consider increasing size: 4096
```

This is still one warning when the value is set to 8192 as tested on my device, instead of many for the default 4096.

Author: ShreckYe

frameworks/Kotlin/vertx-web-kotlinx/vertx-web-kotlinx-postgresql.dockerfile

@@ -28,5 +28,6 @@ CMD export JAVA_OPTS=" \
     -Dio.netty.noUnsafe=false \
     -Dio.netty.buffer.checkBounds=false \
     -Dio.netty.buffer.checkAccessible=false \
+    -Dio.netty.iouring.ringSize=16384 \
     " && \
     build/install/vertx-web-kotlinx-benchmark/bin/vertx-web-kotlinx-benchmark true

frameworks/Kotlin/vertx-web-kotlinx/vertx-web-kotlinx.dockerfile

@@ -28,5 +28,6 @@ CMD export JAVA_OPTS=" \
     -Dio.netty.noUnsafe=false \
     -Dio.netty.buffer.checkBounds=false \
     -Dio.netty.buffer.checkAccessible=false \
+    -Dio.netty.iouring.ringSize=16384 \
     " && \
     build/install/vertx-web-kotlinx-benchmark/bin/vertx-web-kotlinx-benchmark false