Since 1.23.0 ( https://github.com/eclipse-theia/theia/pull/10514 ),
Theia uses socket.io and it needs /socket.io to support websocket,
otherwise it falls back to HTTP polling, which is significantly slower.

https://github.com/eclipse-theia/theia/releases/tag/v1.24.0

See merge request nexedi/slapos!1149

This version of scons only support python2

See merge request nexedi/slapos!1140

no need to prompt everytime. In the context of slapos theia, I guess we
can say that user trust the workspace

This is longer needed since years, also the part looks broken.

Reintroduce a patch to fix build error:

    execvp: printf: Argument list too long

that seems to happen again with nodejs 16.

Also add a note for minimal supported version, that will have to be
set in software

This partially reverts ee733f9d because
of issues with python3

Commit ee733f9d (version up: zc.buildout 2.7.1+slapos017,
slapos.libnetworkcache 0.23, 2022-03-28) introduced a new way of
computing cache key used for shacache and downlaod URLs that were only
in cache but no longer available from their original location no longer
could be retrieved. This update the original download URLs to URLs that
are valid today.

See merge request !1147

I could not find tarball for 2.1 so I updated

also remove useless environment option which has same value as the macro

(+ small cosmetic fixes)