Let users know why they are seeing debug logs in 8.0.0 after upgrading from 6.8.20->7.17.0->8.0.0

[bhavyarm]

Elasticsearch version (bin/elasticsearch --version): 8.0.0

OS version (uname -a if on a Unix-like system): darwin

Description of the problem including expected versus actual behavior: If user upgrades from 6.8.20->7.17.0->8.0.0 ES with both data and config folder - ES displays a bunch of debug logs which are not shown because of #51459 starting 7.7.0

This is how logs look. Can we please tell the user - this is because of the 6.8.20 config file?

2022-01-04T12:53:59,339][DEBUG][o.e.a.s.m.TransportMasterNodeAction] [Bhavyas-MacBook-Pro.local] unexpected exception during publication
org.elasticsearch.ResourceNotFoundException: component template matching [metrics-system.cpu@custom] not found
	at org.elasticsearch.action.admin.indices.template.get.TransportGetComponentTemplateAction.masterOperation(TransportGetComponentTemplateAction.java:86) ~[elasticsearch-8.0.0-SNAPSHOT.jar:8.0.0-SNAPSHOT]
	at org.elasticsearch.action.admin.indices.template.get.TransportGetComponentTemplateAction.masterOperation(TransportGetComponentTemplateAction.java:30) ~[elasticsearch-8.0.0-SNAPSHOT.jar:8.0.0-SNAPSHOT]
	at org.elasticsearch.action.support.master.TransportMasterNodeAction.executeMasterOperation(TransportMasterNodeAction.java:121) ~[elasticsearch-8.0.0-SNAPSHOT.jar:8.0.0-SNAPSHOT]
	at org.elasticsearch.action.support.master.TransportMasterNodeAction$AsyncSingleAction.lambda$doStart$3(TransportMasterNodeAction.java:215) ~[elasticsearch-8.0.0-SNAPSHOT.jar:8.0.0-SNAPSHOT]
	at org.elasticsearch.action.ActionRunnable$2.doRun(ActionRunnable.java:62) ~[elasticsearch-8.0.0-SNAPSHOT.jar:8.0.0-SNAPSHOT]
	at org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:26) [elasticsearch-8.0.0-SNAPSHOT.jar:8.0.0-SNAPSHOT]
	at org.elasticsearch.common.util.concurrent.EsExecutors$DirectExecutorService.execute(EsExecutors.java:220) [elasticsearch-8.0.0-SNAPSHOT.jar:8.0.0-SNAPSHOT]
	at org.elasticsearch.action.support.master.TransportMasterNodeAction$AsyncSingleAction.doStart(TransportMasterNodeAction.java:215) [elasticsearch-8.0.0-SNAPSHOT.jar:8.0.0-SNAPSHOT]
	at org.elasticsearch.action.support.master.TransportMasterNodeAction.doExecute(TransportMasterNodeAction.java:152) [elasticsearch-8.0.0-SNAPSHOT.jar:8.0.0-SNAPSHOT]
	at org.elasticsearch.action.support.master.TransportMasterNodeAction.doExecute(TransportMasterNodeAction.java:52) [elasticsearch-8.0.0-SNAPSHOT.jar:8.0.0-SNAPSHOT]
	at org.elasticsearch.action.support.TransportAction$RequestFilterChain.proceed(TransportAction.java:79) [elasticsearch-8.0.0-SNAPSHOT.jar:8.0.0-SNAPSHOT]
	at org.elasticsearch.action.support.ActionFilter$Simple.apply(ActionFilter.java:53) [elasticsearch-8.0.0-SNAPSHOT.jar:8.0.0-SNAPSHOT]
	at org.elasticsearch.action.support.TransportAction$RequestFilterChain.proceed(TransportAction.java:77) [elasticsearch-8.0.0-SNAPSHOT.jar:8.0.0-SNAPSHOT]
	at org.elasticsearch.xpack.security.action.filt

[bhavyarm]

cc @DaveCTurner Thanks!

[elasticmachine]

Pinging @elastic/es-core-infra (Team:Core/Infra)