RestEasy ServletConfigSourceImpl is broken

[dmlloyd]

Describe the bug
org.jboss.resteasy.microprofile.config.ServletConfigSourceImpl is essentially nonfunctional in a native image. In addition it is context-sensitive which can lead to unexpected behaviors (specifically that two reads of the same key from the same configuration object will yield the same value).

For now I've blacklisted this implementation from being registered to the native image, but it really needs to be revamped or removed.

If we want to support context-sensitive configuration then we need to add that support to Quarkus in such a way that each context gets its own Config instance.

[huw0]

Today I added a custom ConfigSource to my app and suddenly I am getting this stack, which I believe relates to this bug...

java.lang.InstantiationException: Type `org.jboss.resteasy.microprofile.config.ServletConfigSourceImpl` can not be instantiated reflectively as it does not have a no-parameter constructor or the no-parameter constructor has not been added explicitly to the native image.
	at java.lang.Class.newInstance(DynamicHub.java:850)
	at org.jboss.resteasy.microprofile.config.BaseServletConfigSource.<init>(BaseServletConfigSource.java:23)
	at org.jboss.resteasy.microprofile.config.ServletConfigSource.<init>(ServletConfigSource.java:21)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:490)
	at java.util.ServiceLoader$ProviderImpl.newInstance(ServiceLoader.java:779)
	at java.util.ServiceLoader$ProviderImpl.get(ServiceLoader.java:721)
	at java.util.ServiceLoader$3.next(ServiceLoader.java:1394)
	at io.smallrye.config.SmallRyeConfigBuilder.discoverSources(SmallRyeConfigBuilder.java:89)
	at io.smallrye.config.SmallRyeConfig.buildConfigSources(SmallRyeConfig.java:79)
	at io.smallrye.config.SmallRyeConfig.<init>(SmallRyeConfig.java:62)
	at io.smallrye.config.SmallRyeConfigBuilder.build(SmallRyeConfigBuilder.java:359)
	at io.quarkus.runtime.generated.Config.readConfig(Config.zig:1188)
	at io.quarkus.deployment.steps.RuntimeConfigSetup.deploy(RuntimeConfigSetup.zig:42)
	at io.quarkus.runner.ApplicationImpl.doStart(ApplicationImpl.zig:389)
	at io.quarkus.runtime.Application.start(Application.java:90)
	at io.quarkus.runtime.ApplicationLifecycleManager.run(ApplicationLifecycleManager.java:97)
	at io.quarkus.runtime.Quarkus.run(Quarkus.java:62)
	at io.quarkus.runtime.Quarkus.run(Quarkus.java:38)
	at io.quarkus.runtime.Quarkus.run(Quarkus.java:104)
	at io.quarkus.runner.GeneratedMain.main(GeneratedMain.zig:29)

Possibly #9086 also relates.