entrypoints=0.3 rquires flit as build backend

pkgconfig=1.5.1 requires poetry as build backend.

Earlier version 1.22.0 does not support recent setuptools.

Latest version 1.26.2 has more complex build requirements,
left for later.

Now that buildout uses pip to correctly follow pyproject.toml,
cattrs=22.2.0 requires poetry as the build backend.

For now it's easier to install as wheel than to install poetry and
then use it as setup-egg for cattrs. This must be done eventually.

zc.buildout=2.7.1+slapos020 is SlapOS-patched buildout2 with support
for bootstrapping buildout3, required to be able to install buildout3.

Downgrade related eggs to pre-buildout3 versions as well.

Version up zc.buildout, pip and zc.recipe.egg.

Version up slapos.rebootstrap to adapt to buildout3.

Zope no longer serve XML-RPC in ERP5, unless it is explicitly enabled
using this.

See nexedi/erp5!1931

--enable-readline is broken:
  - it searches for readline.h instead of readline/readline.h
  - it does not abort when it fails to find headers
Use --with-readline-inc so that it sets HAVE_READLINE.

Also use the dedicated configure option to enable update limit.
And sqlite3 does not depend directly on ncurses.

See nexedi/neoppod@71564067

See merge request nexedi/slapos!1566

See merge request nexedi/slapos!1576

See merge request nexedi/slapos!1572

to avoid the following error:
relocation R_X86_64_32S against `.rodata' can not be used when making a shared object; recompile with -fPIC

software/osie-coupler: keep the build source directory instead of having another open62541-source part.

This is a fixup of 210e2d76.

Without full diff it's often impossible to understand the problem of JSON
schema introduced by the developer.

Upgrading pygolang in the context of SlapOS brings in some minor speedup
and fixes, but is mostly needed for ors-amarisoft software release due
to fix for a memory leak and optimized timers:

nexedi/pygolang@2ec5e96b
nexedi/pygolang@044deb35

The full list of the changes is below:

nexedi/pygolang@pygolang-0.1...pygolang-0.1-69-g044deb35

/cc ORS team (@jhuge, @lu.xu, @tomo, @xavier_thompson, @Daetalus)
/reviewed-by @jerome
/reviewed-on nexedi/slapos!1569