Responses to POST /_security/api_key includes id, name, metadata,
api_key (shared secret), and encoded (base64 of id:api_key).

Requests to GET /_security/_authenticate returns data about the user,
but not the API KEY.

When authenticating using an API KEY, return API KEY info map in the
response. The initial feature request asked for 'name'. However, the
request's Authentication header contains 'encoded', so the decoded
'id' will be returned for convenience too.

When authenticating using any other method, API KEY info map is
omitted.

Closes elastic#70306

Responses to POST /_security/api_key includes id, name, metadata,
api_key (shared secret), and encoded (base64 of id:api_key).

Requests to GET /_security/_authenticate returns data about the user,
but not the API KEY.

When authenticating using an API KEY, return API KEY info map in the
response. The initial feature request asked for 'name'. However, the
request's Authentication header contains 'encoded', so the decoded
'id' will be returned for convenience too.

When authenticating using any other method, API KEY info map is
omitted.

Closes elastic#70306

# Conflicts:
#	x-pack/plugin/security/src/test/java/org/elasticsearch/xpack/security/authz/store/CompositeRolesStoreTests.java

Fix merge issue.

Fix long lines.

Add a brief message to show when the assertions trip.

Change second assertion from ID to NAME.