Docs: Update multi-get.asciidoc

Duplicate word

Closes #8228
Test: Change missing/null alias test to catch a request error, not a param error

Relates: #7863
Make indexQueryParserService available. Closes #8248
Tests: Refixed the put_alias tests

The missing/null index parameter is in the URL, not the body.
So it should be required, and throw a param error if not provided.

Relates #7863
Introduce elasticsearch.in.bat (i.e. es.in for Windows)

Break-out common functionality between elasticsearch.bat and service.bat
Relates #8237

(cherry picked from commit 87095e79534bcef97b2b275322c924bd96b34e3b)
Improve handling of multicast binding exceptions

In case the multicast binding fails (due to socket errors), abort zen
pinging code and throw a better error message
Relates #8225

(cherry picked from commit f819cff77a0ef95b340afc2f22e3464283803960)
Enabled overriding the request headers in the clients

One can set the headers sent with request by the clients by setting the `request.headers` setting. This commit enables overriding any such set headers directly on the requests.
Use the simpler command line syntax in the Debian init script

It's definitely not a blocker, but it would be nice to be consistent.

Closes #5033
Added missing percolate API parameters (percolate_routing, percolate_preference) to the REST API Spec

Closes #7173
[ENGINE] Add current translog ID to commit meta before closing

Today we simply close the IW when we have to open a new one if ie.
we change merge settings. Yet, the API is deprecated and under the hood
it commits the IW. For safety we should add the current translog ID and
use rollback instead to not wait for merges.
s/MapBuilder/singletonMap in InternalEngine
[TEST] initialize SUITE | GLOBAL scope cluster in a private random context

Today any call to the current randomized context modifies the random
sequence such that cluster initialization is context dependent. If due
to an error for instance a static util method is used like `randomLong`
inside the TestCluster instead of the provided Random instance all
reproducibility guarantees are gone. This commit adds a safe mechanism
to initialize these clusters even if a static helper is used. All none
test scope clusters are now initialized in a private randomized context.
Cut over to randomized runner 2.1.10 and cleanup
ElasticsearchIntegrationTest