Remove mapper attachments plugin

We now have in 5.0.0 `ingest-attachment` plugin.
We can remove `mapper-attachments` plugin for 6.0.

Closes #18837.

Author: dadoonet

buildSrc/src/main/resources/checkstyle_suppressions.xml

@@ -1016,14 +1016,6 @@
   <suppress files="plugins[/\\]lang-python[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]script[/\\]python[/\\]PythonScriptEngineTests.java" checks="LineLength" />
   <suppress files="plugins[/\\]lang-python[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]script[/\\]python[/\\]PythonScriptMultiThreadedTests.java" checks="LineLength" />
   <suppress files="plugins[/\\]lang-python[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]script[/\\]python[/\\]PythonSecurityTests.java" checks="LineLength" />
-  <suppress files="plugins[/\\]mapper-attachments[/\\]src[/\\]main[/\\]java[/\\]org[/\\]elasticsearch[/\\]mapper[/\\]attachments[/\\]AttachmentMapper.java" checks="LineLength" />
-  <suppress files="plugins[/\\]mapper-attachments[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]mapper[/\\]attachments[/\\]DateAttachmentMapperTests.java" checks="LineLength" />
-  <suppress files="plugins[/\\]mapper-attachments[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]mapper[/\\]attachments[/\\]EncryptedDocMapperTests.java" checks="LineLength" />
-  <suppress files="plugins[/\\]mapper-attachments[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]mapper[/\\]attachments[/\\]MetadataMapperTests.java" checks="LineLength" />
-  <suppress files="plugins[/\\]mapper-attachments[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]mapper[/\\]attachments[/\\]MultifieldAttachmentMapperTests.java" checks="LineLength" />
-  <suppress files="plugins[/\\]mapper-attachments[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]mapper[/\\]attachments[/\\]SimpleAttachmentMapperTests.java" checks="LineLength" />
-  <suppress files="plugins[/\\]mapper-attachments[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]mapper[/\\]attachments[/\\]StandaloneRunner.java" checks="LineLength" />
-  <suppress files="plugins[/\\]mapper-attachments[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]mapper[/\\]attachments[/\\]VariousDocTests.java" checks="LineLength" />
   <suppress files="plugins[/\\]mapper-murmur3[/\\]src[/\\]main[/\\]java[/\\]org[/\\]elasticsearch[/\\]index[/\\]mapper[/\\]murmur3[/\\]Murmur3FieldMapper.java" checks="LineLength" />
   <suppress files="plugins[/\\]mapper-murmur3[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]index[/\\]mapper[/\\]murmur3[/\\]Murmur3FieldMapperTests.java" checks="LineLength" />
   <suppress files="plugins[/\\]mapper-murmur3[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]index[/\\]mapper[/\\]murmur3[/\\]Murmur3FieldMapperUpgradeTests.java" checks="LineLength" />

dev-tools/smoke_test_rc.py

@@ -71,7 +71,6 @@
                    "ingest-geoip",
                    "lang-javascript",
                    "lang-python",
-                   "mapper-attachments",
                    "mapper-murmur3",
                    "mapper-size",
                    "repository-azure",