Update to version 26.20.0 and add Clang-CL toolchain flags

[Eragon327]

What does this PR do?

• update to version 26.20.0
• add clang-cl toolchain flags
• implement client version compatibility for command registration in test mode

Which issues does this PR resolve?

Checklist before merging

Thank you for your contribution to the repository.
Before submitting this PR, please make sure:

• Your code builds clean without any errors or warnings
• Your code follows LeviLamina C++ Style Guide
• You have tested all functions
• You have not used code without license
• You have added statement for third-party code

[Eragon327]

没有修改mod的版本号