Add a gerrit config to specify submit requirement columns in dashboard

We add a new "dashboard.submitRequirementColumns" config that can be
defined by gerrit admins to control which submit requirement columns
should appear on the dashboard. If not defined, the default is to
display all submit requirements that are applicable to all changes in
the dashboard.

The new config is also returned as a new field with the "GET
/config/server/info" endpoint.

Google-Bug-Id: b/208609082
Change-Id: I4de5e5c9ff4bd0a412cb703e33939177dc93720b

Documentation/rest-api-config.txt

diff --git a/Documentation/rest-api-config.txt b/Documentation/rest-api-config.txt
index bd93b8b..86d7f58 100644
--- a/Documentation/rest-api-config.txt
+++ b/Documentation/rest-api-config.txt
@@ -2008,6 +2008,10 @@
 |`default_theme`           |optional|
 URL to a default Gerrit UI theme plugin, if available.
 Located in `/static/gerrit-theme.js` by default.
+|`submit_requirement_dashboard_columns` ||
+The list of submit requirement names that should be displayed as separate
+columns in the dashboard. If empty, the default is to display all submit
+requirements that are applicable for changes appearing in the dashboard.
 |=======================================
 
 [[sshd-info]]