Update GraalVM Native Image configuration. (#9515)

Motivation:

The Netty classes are initialized at build time by default for GraalVM Native Image compilation. This is configured via the `--initialize-at-build-time=io.netty` option. While this reduces start-up time it can lead to some problems:

 - The class initializer of `io.netty.buffer.PooledByteBufAllocator` looks at the maximum memory size to compute the size of internal buffers. If the class initializer runs during image generation, then the buffers are sized according to the very large heap size that the image generator uses, and Netty allocates several arrays that are 16 MByte. The fix is to initialize the following 3 classes at run time: `io.netty.buffer.PooledByteBufAllocator,io.netty.buffer.ByteBufAllocator,io.netty.buffer.ByteBufUtil`. This fix was dependent on a GraalVM Native Image fix that was included in 19.2.0.

 - The class initializer of `io.netty.handler.ssl.util.ThreadLocalInsecureRandom` needs to be initialized at runtime to ensure that the generated values are trully random and not fixed for each generated image.

 - The class initializers of `io.netty.buffer.AbstractReferenceCountedByteBuf` and `io.netty.util.AbstractReferenceCounted` compute field offsets. While the field offset recomputation is necessary for correct execution as a native image these initializers also have logic that depends on the presence/absence of `sun.misc.Unsafe`, e.g., via the `-Dio.netty.noUnsafe=true` flag. The fix is to push these initializers to runtime so that the field offset lookups (and the logic depending on them) run at run time. This way no manual substitutions are necessary either.
 
Modifications:

Add `META-INF/native-image` configuration files that correctly trigger the inialization of the above classes at run time via `--initialize-at-run-time=...` flags.
 
Result:

Fixes the initialisation issues described above for Netty executables built with GraalVM.

buffer/src/main/resources/META-INF/native-image/io.netty/buffer/native-image.properties

@@ -0,0 +1,15 @@
+# Copyright 2019 The Netty Project
+#
+# The Netty Project licenses this file to you under the Apache License,
+# version 2.0 (the "License"); you may not use this file except in compliance
+# with the License. You may obtain a copy of the License at:
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+Args = --initialize-at-run-time=io.netty.buffer.PooledByteBufAllocator,io.netty.buffer.ByteBufAllocator,io.netty.buffer.ByteBufUtil,io.netty.buffer.AbstractReferenceCountedByteBuf

common/src/main/resources/META-INF/native-image/io.netty/common/native-image.properties

@@ -0,0 +1,15 @@
+# Copyright 2019 The Netty Project
+#
+# The Netty Project licenses this file to you under the Apache License,
+# version 2.0 (the "License"); you may not use this file except in compliance
+# with the License. You may obtain a copy of the License at:
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+Args = --initialize-at-run-time=io.netty.util.AbstractReferenceCounted

handler/src/main/resources/META-INF/native-image/io.netty/handler/native-image.properties

@@ -0,0 +1,15 @@
+# Copyright 2019 The Netty Project
+#
+# The Netty Project licenses this file to you under the Apache License,
+# version 2.0 (the "License"); you may not use this file except in compliance
+# with the License. You may obtain a copy of the License at:
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+Args = --initialize-at-run-time=io.netty.handler.ssl.util.ThreadLocalInsecureRandom