fixd #1661: fastjson deserialization problem

[fllife]

Describe what this PR does / why we need it

in ModifyRulesCommandHandler linenumber 66:

List<FlowRule> flowRules = JSONArray.parseArray(data, FlowRule.class);
FlowRuleManager.loadRules(flowRules);

when I use fastjson 1.2.7, field resourse and` limitApp can not be set value ，cause config rule not take effect because class AbstractRule do not have setter method

Does this pull request fix one issue?

fixd #1661

Describe how you did it

class AbstractRulemake setter method and not return value

Describe how to verify it

when I use fastjson 1.2.7, filed resourse and limitApp can be set value and config rule can take effect

Special notes for reviews

[CLAassistant]

All committers have signed the CLA.

[fllife]

fixed #1661: fastjson deserialize require a setter method

[jasonjoo2010]

Actually fastjson before 1.2.12 (exclusive) is not usable because it's buggy to those classes having inheritance.
Refer to https://github.com/alibaba/Sentinel/blob/master/sentinel-transport/sentinel-transport-common/src/main/java/com/alibaba/csp/sentinel/command/handler/ModifyRulesCommandHandler.java#L54

And another solution is under progress on these kinds of mess on #1739
You can have a look or do some reviews kindly.

[sczyh30]

Closing this PR due to no further feedback. Thanks for contributing.