[Summer 2021] Seata Registry&Config center metadata simplification

# Background

The current configuration and registry of Seata has a large number of separate configuration items, resulting in high complexity for users to use

# Target

The Seata configuration is converted from configuration items to URLs, reducing multiple metadata information from the previous configuration registry to the form of URLs, and the URL content is parsed by the implementation of each configuration/registry. See the JDBC URL for implementation.

# Difficulty

Easy

# Mentor

@a364176773
364176773@qq.com

# Output Requirements

- Support for one or more configuration or registry resolution URL implementations
- Make sure that non-required configurations have default values

# Technical Requirements

Familiar with Java programming language.
Understand the principles and usage configurations and registries.

# 背景

Seata的当前配置和注册表中存在大量独立的配置项，用户使用起来非常复杂

## 目标

将Seata 配置从配置项转为URL，将之前配置注册中心的多条元数据信息精简为URL形式，每个配置/注册中心的实现解析URL内容。可参照JDBC URL实现.

# 难度

简单

# 导师

@a364176773
364176773@qq.com

# 产出要求

- 支持一个或多个配置或注册表解析URL实现
- 不需要的配置请使用默认值
# 能力要求

熟悉Java编程语言。
了解注册&配置中心的原理和使用配置。

Start by reviewing Seata's existing configuration and registry implementations, then compare their metadata handling with the JDBC URL implementation referenced in the issue. Identify the URL parsing entry points and default handling needed for one or more implementations; done means those URL forms are supported and non-required settings retain defaults.

Written by the indexing model from the issue text.