Refactor parameter definition of DistSQL for feature `shadow`

[RaigorJiang]

Hi community,

This issue is for #18811, to refactor parameter definition in module shardingsphere-shadow-distsql-parser

Aim

• [ ] Redefine identifier and literals in g4 grammar (Literals.g4, Keyword.g4)
• [ ] Change parameter type definitions in g4 of RDLStatement, RQLStatement and RALStatement
• [ ] Update ShadowDistSQLStatementVisitor to fit parameter type adjustment
• [ ] Update parser test cases in module shardingsphere-parser-test
• [ ] Update other affected test cases (Maybe in shardingsphere-integration-test)
• [ ] Update the syntax and usage documentation

Basic Qualifications

• Java
• ANTLR
• Markdown

Links

• Syntax: https://shardingsphere.apache.org/document/current/en/user-manual/shardingsphere-proxy/distsql/syntax/rdl/rule-definition/shadow/
• Usage: https://shardingsphere.apache.org/document/current/en/user-manual/shardingsphere-proxy/distsql/usage/shadow-rule/

Example FYI

#19722