transformer: ecma decorators

[Boshen]

https://github.com/tc39/proposal-decorators?tab=readme-ov-file#how-should-i-use-decorators-in-transpilers-today

esbuild: evanw/esbuild#3754
babel: https://babel.dev/docs/babel-plugin-proposal-decorators#versiont
tsc: https://devblogs.microsoft.com/typescript/announcing-typescript-5-0/#decorators

The conformance suite we should follow is tc39/test262#4103, it should be ready in a month or two, we should help out and provide feedback to it.

I talked to pzuraq (decorators champion), we agree to defer implementing legacy if possible, but actual real world usage require us to implement legacy decorators first (for rolldown).