This adds a force-merge step to the searchable snapshot action, enabled by default,
but parameterizable using the `force_merge-index" optional boolean.
eg.
```
PUT _ilm/policy/my_policy
{
"policy": {
"phases": {
"cold": {
"actions": {
"searchable_snapshot" : {
"snapshot_repository" : "backing_repo",
"force_merge_index": true
}
}
}
}
}
}
```
(cherry picked from commit d0a17b2d35f1b083b574246bdbf3e1929471a4a9)
Signed-off-by: Andrei Dan <andrei.dan@elastic.co>
235e5ed3ea