The api for snapshot/restore was split up between two interfaces,
Repository and IndexShardRepository. There was also complex
initialization and injection between the two. However, there is always a
one to one relationship between the two.
This change moves the IndexShardRepository api into Repository, as well
as updates the API so as not to require any services to be injected for
sublcasses.
Related to #18945 and to this 35d3bdab84 (commitcomment-17914150)
In GCS Repository plugin we defined a `service_account` setting which is defined as `Property.Filtered`.
It's not needed as it's only a path to a file.
Closes#18946
In 2.0 we added plugin descriptors which require defining a name and
description for the plugin. However, we still have name() and
description() which must be overriden from the Plugin class. This still
exists for classpath plugins. But classpath plugins are mainly for
tests, and even then, referring to classpath plugins with their class is
a better idea. This change removes name() and description(), replacing
the name for classpath plugins with the full class name.