Restore "Add more yaml tests for get alias API " (#30814)

These additional tests were previously reverted in 6.x due to failing bwc tests.
They should be skipped against 5.6 nodes, bwc tests fail when the node hit by the request is on 5.6.

Relates to #29513
Relates to #25114
Closes #30806

rest-api-spec/src/main/resources/rest-api-spec/test/indices.get_alias/10_basic.yml

@@ -20,14 +20,58 @@ setup:
 ---
 "Get all aliases via /_alias":
 
+  - do:
+      indices.create:
+        index: test_index_3
+
   - do:
       indices.get_alias: {}
 
   - match: {test_index.aliases.test_alias: {}}
   - match: {test_index.aliases.test_blias: {}}
   - match: {test_index_2.aliases.test_alias: {}}
   - match: {test_index_2.aliases.test_blias: {}}
+  - match: {test_index_3.aliases: {}}
+
+---
+"Get aliases via /_alias/_all":
+  - skip:
+      version: " - 5.99.99"
+      reason:  5.x returns indices that have no aliases
+
+  - do:
+      indices.create:
+        index: test_index_3
+
+  - do:
+      indices.get_alias:
+        name: _all
+
+  - match: {test_index.aliases.test_alias: {}}
+  - match: {test_index.aliases.test_blias: {}}
+  - match: {test_index_2.aliases.test_alias: {}}
+  - match: {test_index_2.aliases.test_blias: {}}
+  - is_false: test_index_3
+
+---
+"Get aliases via /_alias/*":
+  - skip:
+      version: " - 5.99.99"
+      reason:  5.x returns indices that have no aliases
+
+  - do:
+      indices.create:
+        index: test_index_3
 
+  - do:
+      indices.get_alias:
+        name: _all
+
+  - match: {test_index.aliases.test_alias: {}}
+  - match: {test_index.aliases.test_blias: {}}
+  - match: {test_index_2.aliases.test_alias: {}}
+  - match: {test_index_2.aliases.test_blias: {}}
+  - is_false: test_index_3
 
 ---
 "Get all aliases via /{index}/_alias/":