Bump Slf4j API to 2.0.x and drop support for Spring Boot 2

[linghengqian]

Feature Request

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Is your feature request related to a problem?

• For Provides built-in GraalVM Reachability Metadata and nativeTest on Elasticjob Spring Boot Starter under Spring Boot 3.3.2 #2417 .

Describe the feature you would like.

• Bump Slf4j API to 2.0.x and drop support for Spring Boot 2. This obviously avoids defining something like the following in the relevant unit tests of Spring Boot 3.3.2. See https://github.com/apache/shardingsphere-elasticjob/blob/master/test/native/pom.xml .

 <properties>
        <spring-boot-dependencies.version>3.3.2</spring-boot-dependencies.version>
        <slf4j.version>2.0.13</slf4j.version>
        <logback.version>1.5.6</logback.version>
</properties>

• But on the other hand, ShardingSphere itself is still using Slf4j API 1.7.36. And using Slf4j 2.0.x will indeed conflict with Spring Boot 2.x, refer to Restore the slf4j version from 2.0.9 to 1.7.36 before Spring Boot 2 ends the OSS life cycle shardingsphere#29008 and Spring boot 2.7.x does not work with logback 1.3.x (Java 8) spring-projects/spring-boot#34708 .
• Open the current issue to discuss whether we should maintain support for Spring Boot 2.

[linghengqian]

According to apache/shardingsphere#37936 , it seems that this issue no longer needs to consider the ShardingSphere side.