go1.20: add StringData, String, SliceData

[QuLogic]

As a followup to #3391, most of go test passes, except for:

        --- FAIL: TestBuild/Host/rand.go (3.14s)
        --- FAIL: TestBuild/Host/filesystem.go (1.90s)
        --- FAIL: TestBuild/Host/env.go (1.91s)
        --- FAIL: TestBuild/Host/testing.go (8.07s)
        --- FAIL: TestBuild/Host/stdlib.go (3.89s)
        --- FAIL: TestBuild/Host/json.go (5.78s)
        --- FAIL: TestBuild/Host/embed/ (2.08s)

This is due to the following:

    main.go:1174: /usr/lib/golang/src/strings/builder.go:48:39: todo: builtin: SliceData
    main.go:1174: /usr/lib/golang/src/strings/builder.go:48:22: todo: builtin: String
    main.go:1174: /usr/lib/golang/src/strings/clone.go:27:22: todo: builtin: String

Upstream's proposal for this is here: golang/go#53003

According to the release notes, this is a followup to Go 1.17's Slice, so there might be some inspiration from 255f356.

[QuLogic]

Sorry, I forgot to check dev! I see this is implemented already.