Adapt submit requirements names created of plugins' legacy submit rules

We create submit requirement results out of legacy submit records. This
included the evaluation of the default, custom and prolog submit rules
and converting the resulting submit records into submit requirements.

For submit records that have one or more labels, we created a separate
submit requirement result for each label. However if the record
contained no labels, we named the submit requirement after the plugin
name and the implementing class name like:
  $pluginName~$implementingClass

For example, for the code-owners plugin, the corresponding submit
requirement name was created as "code-owners~CodeOwnerSubmitRule" which
is not a user friendly name.

In this change we adapt SubmitRuleEvaluator not to backfill
SubmitRecord#ruleName if it was populated by the plugin. We also added
changes to the code-owners and simple-submit-rules plugins to export the
ruleName with the returned submit records.

Google-Bug-Id: b/211464678
Change-Id: I336c7de83b251cdaef84341a23ab105bff9f39a1
diff --git a/Documentation/user-search.txt b/Documentation/user-search.txt
index 4b593ff..f314e46 100644
--- a/Documentation/user-search.txt
+++ b/Documentation/user-search.txt
@@ -656,8 +656,7 @@
 FORCED}. This means that the submit rule has passed and is not blocking the
 change submission. 'SUBMIT_RULE_NAME' should be in the form of
 '$plugin_name~$rule_name'. For gerrit core rules, 'SUBMIT_RULE_NAME' should
-be in the form of '$rule_name' (example: `DefaultSubmitRule`), or
-'gerrit~$rule_name' (example: `gerrit~DefaultSubmitRule`).
+be in the form of 'gerrit~$rule_name' (example: `gerrit~DefaultSubmitRule`).
 
 rule:'SUBMIT_RULE_NAME'='STATUS'::
 +