Motivation:
At the moment why you try to build a SslContext via SslProvider.OPENSSL* and netty-tcnative* is not on the classpath it will fail with:
```
Exception in thread "main" java.lang.NoClassDefFoundError: io/netty/internal/tcnative/SSLPrivateKeyMethod
at io.netty.handler.ssl.SslContext.newClientContextInternal(SslContext.java:830)
at io.netty.handler.ssl.SslContextBuilder.build(SslContextBuilder.java:611)
at io.netty.handler.codec.http.Main.main(Main.java:34)
Caused by: java.lang.ClassNotFoundException: io.netty.internal.tcnative.SSLPrivateKeyMethod
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:581)
at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522)
... 3 more
```
We should do better here.
Modifications:
Call `OpenSsl.ensureAvailability()` before trying to construct OpenSsl*Context instances
Result:
More clear error message like:
```
java.lang.UnsatisfiedLinkError: failed to load the required native library
at io.netty.handler.ssl.OpenSsl.ensureAvailability(OpenSsl.java:540)
at io.netty.handler.ssl.SslContext.newClientContextInternal(SslContext.java:830)
at io.netty.handler.ssl.SslContextBuilder.build(SslContextBuilder.java:611)
...
Caused by: java.lang.ClassNotFoundException: io.netty.internal.tcnative.SSLContext
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:581)
at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522)
at java.base/java.lang.Class.forName0(Native Method)
at java.base/java.lang.Class.forName(Class.java:398)
at io.netty.handler.ssl.OpenSsl.<clinit>(OpenSsl.java:126)
... 68 more
```
afd812c3a4