[Feature] support separate GM_s/getValue data by container tabs

[ivysrono]

Motivation

GM_openInTab support container tabs, always open tabs by parent tab's container.

For data transmission between different domains, we use GM_setValue not localStorage.

However, by steps below, data does not been separated:

1. setValue('username') = 'A' in containerA
2. setValue('username') = 'B' in containerB
3. getValue('username') in containerA, get 'B' not 'A'.

Proposed Solution

I'm not sure it's Bug or Feature now. Could you support it?

Use Cases

[tophf]

I don't see how we can support it. We can't do it by default because it'll be a breaking change and anyway some scripts want to have a unified storage for all containers.

[ivysrono]

Do it by options?

BTW, could we support data transmission by GM_openInTab + postMessage or other methods?

I tried, failed.

[tophf]

We can add sendMessage function (will return a Promise) and onmessage property to the returned value of GM_openInTab, I guess. The opener will use sendMessage and the second script will use onmessage.
@gera2ld?