Removes all traces of Zen1 from the code base. Some of these commits will also be backported to
7.0/7.x (#39470) as the cluster.coordination package was making use of some things in
discovery.zen and we want to keep 7.x as close as possible to master.
Blob store compression was all implemented generally, except reading the
setting for it. Moved the setting to BlobStoreRepository to unify this.
Also removed deprecated env setting 'repositories.fs.compress'.
This is a follow up on #39073
The removal of the "nGram" and "edgeNGram" token filter was filed in a new
migrate_8_0/mappings.asciidoc document but it should better be in an
analysis.asciidoc section and file.
In #30209 we deprecated the camel case `nGram` filter name in favour of `ngram` and
did the same for `edgeNGram` and `edge_ngram`. Using these names has been deprecated
since 6.4 and is issuing deprecation warnings since then.
I think we can remove these filters in 8.0. In a backport of this PR I would change what was a
dreprecation warning from 6.4. to an error starting with new indices created in 7.0.
Yannick Welsch
Henning Andersen
Christoph Büscher
Tamara Braun