Docs: Update highlighting.asciidoc

Added note about how to highlight on the `_all` field

Closes #7991
Internal: dangling indices import ignores aliases

Dangling indices are indexes found on disk which are not part of the cluster state. By default, we don't delete them but rather import them into the cluster state in order to not accidentally delete data and also allow for the ease of copying index data folders from one cluster to another. Currently, the import logic doesn't check for existing aliases of the same name as the imported dangling index, causing both an index and an alias with the same name.

 This commit add a protection against this. Note that the index is still kept as dangling and is only deleted from disk after `gateway.local.dangling_timeout` has passed (2 hours).

 We also change the log message indicating deletion of dangling indices to a `WARN` level.

 Closes #8059
Docs: Add plugin to list

This plugin provides trigram accelerated regular expression search for when
you need reasonably fast arbitrary matching.

Closes #7997
Adding "min" score mode to parent-child queries

Support for "max", "sum", and "avg" already existed.
Adding ScoreTypesTest missing license header
Add file descriptor details to cat/nodes

cat/nodes currently does not report any details related to file descriptors. This adds the current number in use, the maximum number available as well as their ratio (percentage) to cat/nodes as hidden-by-default metrics. In addition, this also adds current heap usage (as a non-percentage of ts max) and ram usage (as a non-percerntage of its max) to allow tools to provide more granularity.

Closes #7652
Tweaking upgrade test to improve reliability.
testDanglingIndicesConflictWithAlias - wait for node left to be processed

O.w. delete index command may time out waiting for the node that left to confirm deletion
Docs: cross_type query needs to be cross_fields

Closes #8021
Fixing test to allow decimal numbers for load.