remove hardcoded stdlib packages

[xytan0056]

currently the standard list is hardcoded, we can load this from x/tools/go/packages, which is already a dependency.
This means whenever for the same release, different toolchains install could have different the package list. So we don't have to manually maintain this list to include everything stdlib

unit tested

[daixiang0]

I have a question: if we use 1.9 toolchain, users use 1.10, the newer packages cannot be detected, is it right? If so, we can not use this way.

[xytan0056]

I have a question: if we use 1.9 toolchain, users use 1.10, the newer packages cannot be detected, is it right? If so, we can not use this way.

indeed. Maybe I need to reword the PR. But wouldn't we already have this issue with current implementation? The hardcoded list cannot cover all packages, so might as well make it accustomed to users' toolchains. e.g.

func main() {
        pkgs, err := packages.Load(nil, "std")
        if err != nil {
                panic(err)
        }

        fmt.Println(pkgs)
        // go1.16.1 run ./... => 212
        // go1.18.3 run ./... => 233
        // go1.19.4 run ./... => 241
        fmt.Println(len(pkgs)) 
}

I believe when users run go1.x.x install it'll refer to that version

[daixiang0]

You are right, please fix CI then we can get it.

[daixiang0]

@xytan0056 thanks for your contribution!