We were trying to patchelf a file that apparently exists when Theia
is compiled on Debian 8, 10 and 11, but not on Debian 9.

See merge request !1105

Include the hash of all parameters related to the embedded instance
as a comment in the standalone script, so that if the hash changes,
the script and its own hash change as well, and standalone service
will be restarted.

Generate standalone script in instance-theia.cfg.jinja.in instead of
in software.cfg, avoiding the need to forward all the parameters.

Include the hash of the relevant parameters in the abstract socket path,
so that when changing these instance parameters the promise waits until
the standalone service has taken the new parameters into account.

Change "Embedded Instance" to "embedded_instance", and rename existing
"Embdded Instance" into "embedded_instance" for compatibility.

Installing will setup git hooks, so we can do one step further and
also configure the mergetool

otherwise curl uses system ca-certificates if the system package is
installed and otherwise is not able to verify server certificates,
usually being observed in slapos as git refusing to clone with error:
SSL certificate problem: unable to get local issuer certificate

See merge request nexedi/slapos!1103

On Debian 9, the given rpath seem to be ignored when compiling
the `keytar` dependency of theia, for unknown reasons.

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

This was missing in this software and in 03c5b311 (Stop using
hexagonit.recipe.download, 2021-12-03) the hash got out of sync

also mention automatic installation method

Since https://github.com/eclipse-theia/theia/pull/10343 theia depend on
nodejs >= 12 and they test on 12 and 14. Use 14 to have an officially
tested version.

This removes the strong requirement to have python2.7 in theia, so we
just use the software python, which might be python3