This change introduces a new feature for indices so that they can be
hidden from wildcard expansion. The feature is referred to as hidden
indices. An index can be marked hidden through the use of an index
setting, `index.hidden`, at creation time. One primary use case for
this feature is to have a construct that fits indices that are created
by the stack that contain data used for display to the user and/or
intended for querying by the user. The desire to keep them hidden is
to avoid confusing users when searching all of the data they have
indexed and getting results returned from indices created by the
system.
Hidden indices have the following properties:
* API calls for all indices (empty indices array, _all, or *) will not
return hidden indices by default.
* Wildcard expansion will not return hidden indices by default unless
the wildcard pattern begins with a `.`. This behavior is similar to
shell expansion of wildcards.
* REST API calls can enable the expansion of wildcards to hidden
indices with the `expand_wildcards` parameter. To expand wildcards
to hidden indices, use the value `hidden` in conjunction with `open`
and/or `closed`.
* Creation of a hidden index will ignore global index templates. A
global index template is one with a match-all pattern.
* Index templates can make an index hidden, with the exception of a
global index template.
* Accessing a hidden index directly requires no additional parameters.
Backport of #50452
107989df3e