[Dashboard bug] When the method of saveAll (List rules) is called , InMemoryRuleRepositoryAdapter will clear all historical rules, but you don't save the new rules.

## Issue Description

Type: *bug report*

### Describe what happened (or what feature you want)
When calling the saveAll InMemoryRuleRepositoryAdapter () method, can clear rules of the original data, however, did not save the new data.

**InMemoryRuleRepositoryAdapter.java**
```
@Override
public List saveAll(List rules) {
// TODO: check here.
allRules.clear();
machineRules.clear();
appRules.clear();

if (rules == null) {
return null;
}
List savedRules = new ArrayList<>(rules.size());
for (T rule : rules) {
savedRules.add(save(rule));
}
return savedRules;
}
```

### Describe what you expected to happen

Sentinel dashboard rules are persisted to Apollo.

Saving a new rule after dashboard restarts will result in loss of historical data.

### How to reproduce it (as minimally and precisely as possible)

1. First,the application has some saved rules.
2. Restart the sentinel dashboard.
3. Add a rule of this application,it can be any type of rules.
4. You will find that a piece of data is missing from the history rule after you saved a new rule item.

### Tell us your environment

Sentinel 1.8.0.
Integration with Apollo dynamic data source.
Extends the ability to persist Dashboard rules to Apollo.

### Anything else we need to know?
Save the new rules after clear them.

**InMemoryRuleRepositoryAdapter.java**
```
@Override
public List saveAll(List rules) {
// TODO: check here.
allRules.clear();
machineRules.clear();
appRules.clear();

if (rules == null) {
return null;
}
List savedRules = new ArrayList<>(rules.size());
for (T rule : rules) {
//add. save new rules
T processedEntity = preProcess(rule);
if (processedEntity != null) {
allRules.put(processedEntity.getId(), processedEntity);
machineRules.computeIfAbsent(MachineInfo.of(processedEntity.getApp(), processedEntity.getIp(),
processedEntity.getPort()), e -> new ConcurrentHashMap<>(32))
.put(processedEntity.getId(), processedEntity);
appRules.computeIfAbsent(processedEntity.getApp(), v -> new ConcurrentHashMap<>(32))
.put(processedEntity.getId(), processedEntity);
}
savedRules.add(save(rule));
}
return savedRules;
}

```

Start with InMemoryRuleRepositoryAdapter.java and inspect the saveAll(List rules) entry point, including its clearing and saving behavior. Reproduce the restart-and-save sequence described in the issue; done means historical rules remain available while the new rules are saved.

Written by the indexing model from the issue text.