software/theia: Version up 1.28.0 and fix IPv6 url

Resolve `@theia/core` subdependency `vscode-uri` to a locally installed patched version, to workaround https://github.com/microsoft/vscode/issues/154048.

This fixes access to Theia through the IPv6 `backend-url`. That issue was discussed in nexedi/slapos!1204

The patched version of `vscode-uri` is published here: https://github.com/xavth/vscode-uri/tree/fix/ipv6_url_authority

To do this, `yarn.lock` was regenerated, so this also caused a version up to Theia 1.28.0.

See merge request nexedi/slapos!1227