Add applies_to tags to ES troubleshooting (elastic#968)

First pass based on advice from @DaveCTurner (thanks!): add standard set
of applies_to tags to ES troubleshooting

plus some incidental sprucing.

Preview: everything in
[Elasticsearch](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/968/troubleshoot/elasticsearch)
except for section overviews and such

Author: marciw

troubleshoot/elasticsearch/add-tier.md

@@ -1,4 +1,11 @@
 ---
+applies_to:
+  stack: 
+  deployment:
+    eck: 
+    ess: 
+    ece: 
+    self: 
 navigation_title: Preferred data tier
 mapped_pages:
   - https://www.elastic.co/guide/en/elasticsearch/reference/current/add-tier.html

troubleshoot/elasticsearch/allow-all-cluster-allocation.md

@@ -1,4 +1,11 @@
 ---
+applies_to:
+  stack: 
+  deployment:
+    eck: 
+    ess: 
+    ece: 
+    self: 
 navigation_title: Data allocation
 mapped_pages:
   - https://www.elastic.co/guide/en/elasticsearch/reference/current/allow-all-cluster-allocation.html

troubleshoot/elasticsearch/allow-all-index-allocation.md

@@ -1,4 +1,11 @@
 ---
+applies_to:
+  stack: 
+  deployment:
+    eck: 
+    ess: 
+    ece: 
+    self: 
 navigation_title: Index allocation
 mapped_pages:
   - https://www.elastic.co/guide/en/elasticsearch/reference/current/allow-all-index-allocation.html

troubleshoot/elasticsearch/circuit-breaker-errors.md

@@ -1,4 +1,11 @@
 ---
+applies_to:
+  stack: 
+  deployment:
+    eck: 
+    ess: 
+    ece: 
+    self: 
 mapped_pages:
   - https://www.elastic.co/guide/en/elasticsearch/reference/current/circuit-breaker-errors.html
 ---

troubleshoot/elasticsearch/corruption-troubleshooting.md

@@ -1,4 +1,11 @@
 ---
+applies_to:
+  stack: 
+  deployment:
+    eck: 
+    ess: 
+    ece: 
+    self: 
 navigation_title: Data corruption
 mapped_pages:
   - https://www.elastic.co/guide/en/elasticsearch/reference/current/corruption-troubleshooting.html

troubleshoot/elasticsearch/decrease-disk-usage-data-node.md

@@ -1,4 +1,11 @@
 ---
+applies_to:
+  stack: 
+  deployment:
+    eck: 
+    ess: 
+    ece: 
+    self: 
 navigation_title: Decrease disk usage
 mapped_pages:
   - https://www.elastic.co/guide/en/elasticsearch/reference/current/decrease-disk-usage-data-node.html

troubleshoot/elasticsearch/diagnose-unassigned-shards.md

@@ -1,4 +1,11 @@
 ---
+applies_to:
+  stack: 
+  deployment:
+    eck: 
+    ess: 
+    ece: 
+    self: 
 navigation_title: Unassigned shards
 mapped_pages:
   - https://www.elastic.co/guide/en/elasticsearch/reference/current/diagnose-unassigned-shards.html

troubleshoot/elasticsearch/diagnosing-corrupted-repositories.md

@@ -1,4 +1,11 @@
 ---
+applies_to:
+  stack: 
+  deployment:
+    eck: 
+    ess: 
+    ece: 
+    self: 
 navigation_title: Corrupted repositories
 mapped_pages:
   - https://www.elastic.co/guide/en/elasticsearch/reference/current/diagnosing-corrupted-repositories.html

troubleshoot/elasticsearch/diagnosing-invalid-repositories.md

@@ -1,4 +1,11 @@
 ---
+applies_to:
+  stack: 
+  deployment:
+    eck: 
+    ess: 
+    ece: 
+    self: 
 navigation_title: Invalid repositories
 mapped_pages:
   - https://www.elastic.co/guide/en/elasticsearch/reference/current/diagnosing-invalid-repositories.html

troubleshoot/elasticsearch/diagnosing-unknown-repositories.md

@@ -1,4 +1,11 @@
 ---
+applies_to:
+  stack: 
+  deployment:
+    eck: 
+    ess: 
+    ece: 
+    self: 
 navigation_title: Unknown repositories
 mapped_pages:
   - https://www.elastic.co/guide/en/elasticsearch/reference/current/diagnosing-unknown-repositories.html