API Changes

[undefined-moe]

本 issue 列出计划进行的重大 API 更改。
This thread will announce the planned breaking API changes.

• sync with cordis upstream: ctx.using -> ctx.inject, ctx.inject -> ctx.injectUI (drop legacy support in next major version)
• drop legacy plugin format (handler.ts) in next major version
• vjudge: move to judge client side (calls to some builtin model will be prohibited, refactor will be required)
• Hydro Global Variable: drop in next major version. Use context instead.
• Introduce checksum to installed plugins

如果对如上修改有任何的建议，请在下方评论。
If you have any suggestions to those, comment below.