fix: add serial comparison in DConfigCacheImpl::setValue

1. Add serial comparison condition to setValue() so cache is
   updated when serial differs even if value is the same
2. Update two setValue() doc comments to reflect new return
   value semantics

Log: Fixed dconfig write failure after serial upgrade

Influence:
1. Test dconfig setValue with same value but different serial
2. Verify cache updates correctly when serial changes
3. Test that setValue returns false only when both value and
   serial match

fix: DConfigCacheImpl::setValue增加serial比较条件

1. setValue()方法增加serial比较条件，当serial不一致时
   强制更新缓存
2. 更新两处setValue()文档注释，说明返回值的新语义

Log: 修复dconfig serial升级后写入相同值失败的问题

Influence:
1. 测试dconfig在serial不同但值相同时的setValue行为
2. 验证serial变更时缓存是否正确更新
3. 测试setValue仅在值和serial都匹配时返回false

Author: deepin-wm

src/dconfigfile.cpp

@@ -985,7 +985,7 @@ DConfigMetaImpl::~DConfigMetaImpl()
     \a value Configuration name
     \a uid User Id at setup time
     \a callerAppid Application id at setup time
-    @return A value of true indicates that the new value has been reset, and false indicates that it has not been set
+    @return true if the cache was updated (value or serial changed), false if no update was needed
 */
 
 /*!
@@ -1124,7 +1124,7 @@ class Q_DECL_HIDDEN DConfigCacheImpl : public DConfigCache {
     }
     bool setValue(const QString &key, const QVariant &value, const int serial, const uint uid, const QString &appid) override
     {
-        if (values.value(key) == value) {
+        if (values.value(key) == value && values.serial(key) == serial) {
             return false;
         }
         values.setValue(key, value);
@@ -1487,7 +1487,7 @@ QVariant DConfigFile::cacheValue(DConfigCache *userCache, const QString &key) co
     \a value The value to set
     \a userCache Specific user cache at setup time
     \a appid Application id at setup time
-    @return A value of true indicates that the new value has been reset, and false indicates that it has not been set
+    @return true if the cache was updated (value or serial changed), false if no update was needed
  */
 bool DConfigFile::setValue(const QString &key, const QVariant &value, const QString &callerAppid, DConfigCache *userCache)
 {