Explicit variance annotations for built-in .d.ts files

While profiling some projects using typeslayer, I've noticed that according to the type checking traces some time is spent calculating the type variance of common types like Promise<T> and others.

I've explicitly annotated some of these generic types, and I've verified that it that sped up typechecking for some of my complex use-cases.
I've verified that these speed-ups also translate to tsgo by checking with hyperfine.

I'd like to ask if a PR to add explicit type variance to some of the most commonly used library types could be a valuable addition? I could set up a PR so some performance tests could be run to see if it works in aggregate, I just wanted to ask if it's something that aligns with the projects' goals and to maybe understand if this was tried already

Based on my limited understanding the pros would be:

• More people learning about variance and explicit variance annotations
• Slightly increased performance in some complex scenarios

The cons would be:

• Different error messages as now we'd see super and sub prefixes that might confuse users
• larger size on the wire/disk
• higher overhead to parse

未指定源文件或测试。首先检查内置的 .d.ts 库类型以及 issue 中描述的类型检查跟踪，然后将 tsgo 的测量结果与 hyperfine 进行比较。完成的标准是就常用的目标类型达成一致，并通过性能测试展示其对整体性能和诊断的影响。