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 https://lab.nexedi.com/nexedi/slapos/merge_requests/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.