Remove DEBUG-level default logging from actions

In 2bb31fe (v0.6.0!) we added DEBUG-level logging to the default config of
action loggers "for easier debugging". This change to the default config lives
on to this day. It does not obviously make debugging any easier any more, but
it does result in a good deal of log noise sometimes. This commit removes this
special case from the default config.

Closes elastic#51198

distribution/src/config/log4j2.properties

@@ -1,9 +1,5 @@
 status = error
 
-# log action execution errors for easier debugging
-logger.action.name = org.elasticsearch.action
-logger.action.level = debug
-
 appender.console.type = Console
 appender.console.name = console
 appender.console.layout.type = PatternLayout

docs/reference/migration/migrate_7_7.asciidoc

@@ -0,0 +1,33 @@
+[[breaking-changes-7.7]]
+== Breaking changes in 7.7
+++++
+<titleabbrev>7.7</titleabbrev>
+++++
+
+This section discusses the changes that you need to be aware of when migrating
+your application to Elasticsearch 7.7.
+
+See also <<release-highlights>> and <<es-release-notes>>.
+
+coming[7.7.0]
+
+//NOTE: The notable-breaking-changes tagged regions are re-used in the
+//Installation and Upgrade Guide
+
+//tag::notable-breaking-changes[]
+
+//end::notable-breaking-changes[]
+
+[discrete]
+[[breaking_77_logging_changes]]
+=== Logging changes
+
+[discrete]
+==== Loggers under `org.elasticsearch.action` now log at `INFO` level by default
+
+The default log level for most loggers is `INFO`, but in earlier versions
+loggers in the `org.elasticsearch.action.*` hierarchy emitted log messages at
+`DEBUG` level by default. This sometimes resulted in a good deal of unnecessary
+log noise. From 7.7 onwards the default log level for logger in this hierarchy
+is now `INFO`, in line with most other loggers. If needed, you can recover the
+pre-7.7 default behaviour by adjusting your <<logging>>.