[DOCS] Move migration APIs to docs (#31473)

Author: lcawl

x-pack/docs/en/rest-api/migration/assistance.asciidoc renamed to docs/reference/migration/apis/assistance.asciidoc

@@ -1,4 +1,5 @@
 [role="xpack"]
+[testenv="basic"]
 [[migration-api-assistance]]
 === Migration Assistance API
 

x-pack/docs/en/rest-api/migration/deprecation.asciidoc renamed to docs/reference/migration/apis/deprecation.asciidoc

@@ -1,4 +1,5 @@
 [role="xpack"]
+[testenv="basic"]
 [[migration-api-deprecation]]
 === Deprecation Info APIs
 

x-pack/docs/en/rest-api/migration/upgrade.asciidoc renamed to docs/reference/migration/apis/upgrade.asciidoc

@@ -1,4 +1,5 @@
 [role="xpack"]
+[testenv="basic"]
 [[migration-api-upgrade]]
 === Migration Upgrade API
 

x-pack/docs/en/rest-api/migration.asciidoc renamed to docs/reference/migration/migration.asciidoc

@@ -1,4 +1,5 @@
 [role="xpack"]
+[testenv="basic"]
 [[migration-api]]
 == Migration APIs
 
@@ -8,6 +9,6 @@ The migration APIs simplify upgrading {xpack} indices from one version to anothe
 * <<migration-api-upgrade>>
 * <<migration-api-deprecation>>
 
-include::migration/assistance.asciidoc[]
-include::migration/upgrade.asciidoc[]
-include::migration/deprecation.asciidoc[]
+include::apis/assistance.asciidoc[]
+include::apis/upgrade.asciidoc[]
+include::apis/deprecation.asciidoc[]

docs/reference/rest-api/index.asciidoc

@@ -21,7 +21,7 @@ directly to configure and access {xpack} features.
 include::info.asciidoc[]
 include::{xes-repo-dir}/rest-api/graph/explore.asciidoc[]
 include::{es-repo-dir}/licensing/index.asciidoc[]
-include::{xes-repo-dir}/rest-api/migration.asciidoc[]
+include::{es-repo-dir}/migration/migration.asciidoc[]
 include::{xes-repo-dir}/rest-api/ml-api.asciidoc[]
 include::{xes-repo-dir}/rest-api/rollup-api.asciidoc[]
 include::{xes-repo-dir}/rest-api/security.asciidoc[]