[8.1] Move internal APIs into their own namespace '_internal' (#83678)

Author: sethmlarson

rest-api-spec/src/main/resources/rest-api-spec/api/desired_nodes.delete_desired_nodes.json renamed to rest-api-spec/src/main/resources/rest-api-spec/api/_internal.delete_desired_nodes.json

@@ -1,10 +1,10 @@
 {
-  "desired_nodes.delete_desired_nodes":{
+  "_internal.delete_desired_nodes":{
     "documentation":{
       "url":"https://www.elastic.co/guide/en/elasticsearch/reference/current/delete-desired-nodes.html",
       "description": "Deletes the desired nodes. Designed for indirect use by ECE/ESS and ECK. Direct use is not supported."
     },
-    "stability":"stable",
+    "stability":"experimental",
     "visibility":"private",
     "headers":{
       "accept": [ "application/json"]

rest-api-spec/src/main/resources/rest-api-spec/api/desired_nodes.get_desired_nodes.json renamed to rest-api-spec/src/main/resources/rest-api-spec/api/_internal.get_desired_nodes.json

@@ -1,10 +1,10 @@
 {
-  "desired_nodes.get_desired_nodes":{
+  "_internal.get_desired_nodes":{
     "documentation":{
       "url":"https://www.elastic.co/guide/en/elasticsearch/reference/current/get-desired-nodes.html",
       "description": "Gets the latest desired nodes. Designed for indirect use by ECE/ESS and ECK. Direct use is not supported."
     },
-    "stability":"stable",
+    "stability":"experimental",
     "visibility":"private",
     "headers":{
       "accept": [ "application/json"]

rest-api-spec/src/main/resources/rest-api-spec/api/desired_nodes.update_desired_nodes.json renamed to rest-api-spec/src/main/resources/rest-api-spec/api/_internal.update_desired_nodes.json

@@ -1,10 +1,10 @@
 {
-  "desired_nodes.update_desired_nodes":{
+  "_internal.update_desired_nodes":{
     "documentation":{
       "url":"https://www.elastic.co/guide/en/elasticsearch/reference/current/update-desired-nodes.html",
       "description": "Updates the desired nodes. Designed for indirect use by ECE/ESS and ECK. Direct use is not supported."
     },
-    "stability":"stable",
+    "stability":"experimental",
     "visibility":"private",
     "headers":{
       "accept": [ "application/json"],

rest-api-spec/src/main/resources/schema.json

@@ -6,12 +6,12 @@
         "Api": {
             "type": "object",
             "propertyNames": {
-                "pattern": "^[a-z]+?(_[a-z]+)*(\\.[a-z]+?(_[a-z]+)*)?$"
+                "pattern": "^(?:[a-z]+?(_[a-z]+)*(\\.[a-z]+?(_[a-z]+)*)?|_internal\\.[a-z]+?(_[a-z]+)*)$"
             },
             "minProperties": 1,
             "maxProperties": 1,
             "patternProperties": {
-                "^[a-z]+?(_[a-z]+)*(\\.[a-z]+?(_[a-z]+)*)?$": {
+                "^(?:[a-z]+?(_[a-z]+)*(\\.[a-z]+?(_[a-z]+)*)?|_internal\\.[a-z]+?(_[a-z]+)*)$": {
                     "$ref": "#/definitions/Components"
                 }
             },