[Feature] implement MD5() functions

[Asolmn]

What type of PR is this?

• API-change
• BUG
• Improvement
• Documentation
• Feature
• Test and CI
• Code Refactoring

Which issue(s) this PR fixes:

issue #15096

What this PR does / why we need it:

add md5() functions
ref: https://dev.mysql.com/doc/refman/8.0/en/encryption-functions.html#function_md5

[CLAassistant]

All committers have signed the CLA.

[matrix-meow]

@Asolmn Thanks for your contributions!

Pull Request Review:

Title: [Feature] implement MD5() functions

Body:

• The PR is categorized as a Feature.
• It references and aims to resolve issue [Feature Request]: MD5 and SHA1 #15096 on GitHub.
• The purpose of this PR is to add MD5() functions to the codebase, with a reference to the MySQL documentation for MD5 functions.

Changes:

1. func_unary.go:

   • Added crypto/md5 import.
   • Added Md5 function that calculates MD5 hash of input data.
   • Added test cases for the Md5 function.

2. func_unary_test.go:

   • Added test cases for the Md5 function.

3. function_id.go:

   • Added MD5 constant to the functionIdRegister map.

4. list_builtIn.go:

   • Added Md5 function definition to the list of supported functions.

5. func_md5.result and func_md5.sql:

   • Added test cases and expected results for the Md5 function.

Feedback and Suggestions:

1. Security Concerns:
   • Avoid Using MD5 for Cryptographic Purposes: MD5 is considered cryptographically broken and should not be used for security-sensitive applications. Consider using more secure hashing algorithms like SHA-256.
   • Input Validation: Ensure proper input validation in