Add l10n ownership/site config updates to all production branches

[zacharysarah]

This is a...

• Feature Request
• Bug Report

Problem

#10485 included significant changes to site support and structure for localization (l10n). We need to port the site configuration changes from #10485 to each current production branch:

release-1.12
release-1.11
release-1.10

Proposed solution

I'd like to divide the work of sourcing l10n content for production branches into two distinct pieces:

1. Site config and permissions (@zacharysarah)

2. Adding version-specific l10n content to each production branch (l10n teams)

Site config and permissions

We can resolve 1.12 by merging master into release-1.12. 👈 @tfogo

I'll open 2 additional pull requests, one for 1.11 and 1.10, to configure site support and branch ownership so that different l10n teams can start merging their own source into the various release branches.

Things l10n teams will handle: migrating content

Once the PRs for site config merge ☝️, l10n teams can start opening, reviewing, and approving PRs to add or update version-specific localized content to release branches.

Normally we don't allow PRs for previous versions, but in this case, it makes sense to allow exceptions.

If there aren't any source files for a specific version, no problem.

@markthink, @hanjiayao Specifically for Chinese content: #10485 included changing the directory structure for localized Chinese content from content/cn/ to content/zh/. After this PR merges, please make sure that any content migration PRs ☝️ reflect the change in source structure.

/cc
@kubernetes/sig-docs-en-owners
@kubernetes/sig-docs-ja-owners
@kubernetes/sig-docs-ko-owners
@kubernetes/sig-docs-zh-owners

[zacharysarah]

Fixed by #10667 and #10668.