Support inheriting project submit type

Change Project to only expose the configured submit type for that
project, and modify all callers to call the equivalent method on
ProjectState which respects inheritance.

In the extension/REST API, expose the inherited submit type analogously
to the inherited boolean values, using an object containing configured
and inherited values. For backwards compatibility, leave the old
submit_type field as-is, but mark it deprecated, in the hopes that we
can eventually replace it.

Do not change the default of a project with no configured submit type,
leaving the default as MERGE_IF_NECESSARY. This avoids, for now, the
need for migrating existing projects that do not have a submit type set,
including those that were created outside of Gerrit and don't have
refs/meta/config at all.

After this change, the global `repository.<name>.defaultSubmitType`
configuration still takes effect when creating a new project. A later
change may remove support for defaultSubmitType, but the migration to
convert global config into appropriate inheritable config values is
nontrivial, so we're punting on it.

Change-Id: Ib5711baaa67b2c92239a1ff4564349a80d211c28

java/com/google/gerrit/extensions/api/projects/ConfigInfo.java

@@ -37,7 +37,9 @@ public class ConfigInfo {
   public InheritedBooleanInfo matchAuthorToCommitterDate;
 
   public MaxObjectSizeLimitInfo maxObjectSizeLimit;
+  @Deprecated // Equivalent to defaultSubmitType.value
   public SubmitType submitType;
+  public SubmitTypeInfo defaultSubmitType;
   public ProjectState state;
   public Map<String, Map<String, ConfigParameterInfo>> pluginConfig;
   public Map<String, ActionInfo> actions;
@@ -72,4 +74,10 @@ public class ConfigInfo {
     public List<String> permittedValues;
     public List<String> values;
   }
+
+  public static class SubmitTypeInfo {
+    public SubmitType value;
+    public SubmitType configuredValue;
+    public SubmitType inheritedValue;
+  }
 }

java/com/google/gerrit/extensions/client/SubmitType.java

@@ -15,10 +15,11 @@
 package com.google.gerrit.extensions.client;
 
 public enum SubmitType {
+  INHERIT,
   FAST_FORWARD_ONLY,
   MERGE_IF_NECESSARY,
   REBASE_IF_NECESSARY,
   REBASE_ALWAYS,
   MERGE_ALWAYS,
-  CHERRY_PICK
+  CHERRY_PICK;
 }