### Description

Implement health indicator for shard allocation.
This indicator should have same or similar behavior to existing health endpoint.

Aspects to be considered:
* nodes scheduled for reboot should not cause cluster to go yellow (but could cause it go red)
* huge number of unallocated shards should not cause response bloat.
* consider showing allocation explain if possible

Rel: TBD
server/src/main/java/org/elasticsearch/node/Node.java
deprecationLogger.warn(
                    DeprecationCategory.OTHER,
                    "no-jdk",
                    "no-jdk distributions that do not bundle a JDK are deprecated and will be removed in a future release"
                );
            }
            logger.info("JVM arguments {}", Arrays.toString(jvmInfo.getInputArguments()));
            if (Build.CURRENT.isProductionRelease() == false) {
                logger.warn(
                    "version [{}] is a pre-release version of Elasticsearch and is not suitable for production",
                    Build.CURRENT.qualifiedVersion()
                );
            }
            if (Environment.PATH_SHARED_DATA_SETTING.exists(tmpSettings)) {
                
                
                deprecationLogger.warn(
                    DeprecationCategory.SETTINGS,
                    "shared-data-path",
                    "setting [path.shared_data] is deprecated and will be removed in a future release"
                );
            }
            if (initialEnvironment.dataFiles().length > 1) {
                
                deprecationLogger.warn(
                    DeprecationCategory.SETTINGS,
                    "multiple-data-paths",
                    "Configuring multiple [path.data] paths is deprecated. Use RAID or other system level features for utilizing "
                        + "multiple disks. This feature will be removed in a future release."
                );