WIP - language status for partial mode

[jrieken]

When running in a limited context, like github.dev, it should be made clear that language support isn't at the same level as in desktop or codespaces. With TypeScript and anycode we have settled on some best practice and wording. This PR is WIP towards that uniform UX/language (more details at https://github.com/microsoft/vscode-dev/issues/300)

There is still a few open questions, namely

• the wording for "details" needs to be tweaked
• create aka.ms-link for the "Learn More" and fill it with content
• (engineering) I wasn't able to use the localize-util, importing src/client/common/utils/localize.ts fails to webpack
• (engineering) unsure if I am updating/using that API proposal correcty

[karthiknadig]

@jrieken Thanks for looking into this, we have a PR (#17658) up for this that @karrtikr is taking care of the wording with the pylance team.