Always require native libraries for running tests (#2990)

Motivation:

In rare occasions tests may fail with ambiguous errors. After hours of
debugging, the root cause may end up an inability to load native
libraries.

Modifications:

- Enforce `io.servicetalk.transport.netty.requireNativeLibs=true` for
running tests.

Result:

Significantly simplifies finding the root cause for hanging tests.

servicetalk-gradle-plugin-internal/src/main/groovy/io/servicetalk/gradle/plugin/internal/ServiceTalkLibraryPlugin.groovy

@@ -229,6 +229,10 @@ final class ServiceTalkLibraryPlugin extends ServiceTalkCorePlugin {
 
         jvmArgs "-server", "-Xms2g", "-Xmx4g", "-dsa", "-da", "-ea:io.servicetalk...",
                 "-XX:+HeapDumpOnOutOfMemoryError"
+
+        // Always require native libraries for running tests. This helps to make sure transport-level state machine
+        // receives all expected network events from Netty.
+        systemProperty "io.servicetalk.transport.netty.requireNativeLibs", "true"
       }
 
       dependencies {