Configure errorprone's ClassInitializationDeadlock (#7021)

This ensures we do not introduce new cases of this issue by failing the build when they are detected by ErrorProne.
It suppresses the warning on the existing cases we are aware of while we separately decide what to do about them.

See gh-6998

Signed-off-by: Emanuel Trandafir <emanueltrandafir1993@gmail.com>

Author: etrandafir93

build.gradle

@@ -98,6 +98,7 @@ subprojects {
                     "BadImport",
                     "CatchAndPrintStackTrace",
                     "ClassCanBeStatic",
+                    "ClassInitializationDeadlock",
                     "CollectionUndefinedEquality",
                     "DefaultCharset",
                     "DoNotCallSuggester",

micrometer-observation/src/main/java/io/micrometer/observation/Observation.java

@@ -52,6 +52,7 @@ public interface Observation extends ObservationView {
      * No-op observation. Do not use it to check if an Observation is no-op, use
      * {@code observation.isNoop()} instead.
      */
+    @SuppressWarnings("ClassInitializationDeadlock")
     Observation NOOP = NoopObservation.INSTANCE;
 
     /**
@@ -837,6 +838,7 @@ interface Scope extends AutoCloseable {
         /**
          * No-op scope.
          */
+        @SuppressWarnings("ClassInitializationDeadlock")
         Scope NOOP = NoopObservation.NoopScope.INSTANCE;
 
         /**

micrometer-observation/src/main/java/io/micrometer/observation/ObservationRegistry.java

@@ -45,6 +45,7 @@ static ObservationRegistry create() {
     /**
      * No-op implementation of {@link ObservationRegistry}.
      */
+    @SuppressWarnings("ClassInitializationDeadlock")
     ObservationRegistry NOOP = new NoopObservationRegistry();
 
     /**