- Move [theia] section and dependencies into component/theia
- Make [theia] section shared

To have the timeline view

The golang.go extension can overwrite the shell environment PATH,
which can break the shell.

Some old version of plugins have been removed from openvsx when they
changed licence. Uploaders who did not sign the licence had their extensions
removed. This was the case for some builtin vscode extensions uploaded by
openvsx script.

use "latest" in generate_download_plugins_cfg.py, so that re-running this
script updates plugins to their latest versions.

slapos.recipe.build verifies signatures of downloaded files and can also use
buildout cache or download from shacache, which

This introduces a new download-plugins.cfg, containing the URLs of
extensions and their md5sum signatures. This profile is extended by
software.cfg and there's a section using slapos.recipe.build to actually
download extensions.

A generate_download_plugins_cfg.py python script is also included, to be
run by software release maintainers to update download-plugins.cfg using the
list of plugins included in generate_download_plugins_cfg.py