This commit adds the initial document for version two index templates. Since these are intended to
be used in favor of V1 index templates, this re-uses the anchors for index templates to point to the
V2 APIs, renaming the V1 template docs' anchors (this was a suggestion from the docs team).
There is more documentation that can be written, but this is a start.
Relates to #53101
The docs tests have recently been running much slower than before (see #49753).
The gist here is that with ILM/SLM we do a lot of unnecessary setup / teardown work on each
test. Compounded with the slightly slower cluster state storage mechanism, this causes the
tests to run much slower.
In particular, on RAMDisk, docs:check is taking
ES 7.4: 6:55 minutes
ES master: 16:09 minutes
ES with this commit: 6:52 minutes
on SSD, docs:check is taking
ES 7.4: ??? minutes
ES master: 32:20 minutes
ES with this commit: 11:21 minutes
James Rodewig
debadair
Lisa Cawley
Lee Hinman
Yannick Welsch
Julie Tibshirani
James Rodewig